InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
The intersect cuts-off by a line from y-axis is twice that from x-axis and the line passes through the point (1, 2). Find the equation of the line |
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Answer» The equation of a line intercept form is \(\frac{x}{a}+\frac{y}{b}=1\) Given, b = 2 ∴ (1) ⇒ \(\frac{x}{a}+\frac{y}{2a}=1\) ⇒ 2x + y = 2α Since the line passes though the point (1, 2), 2. 1 + 2 = 2a ⇒ a = 2 ∴ Equation of the line is 2x + y – 4 = 0. |
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| 102. |
Find the equation of the line passing through the point ( – 3, 5) and perpendicular to the line joining (2, 5) and ( – 3, 6). |
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Answer» Given, A line which passes through the point ( – 3,5) and perpendicular to the line joining (2,5) and ( – 3,6) To Find: Find the equation Formula Used: The equation of line is (y – y1) = m(x – x1) Explanation: Here, The line passes through the point ( – 3,5 ), Given So, The coordinate (x1,y1) = ( – 3,5) Now, The line is perpendicular to the line joining (2,5) and ( – 3,6), We know, The slope of the line with two points is, m = \(\frac{y_2 -y_1}{x_2-x_1}\) So, the slope of line joining (2, 5 ) and ( – 3,6) is = \(\frac{6-5}{-3-2}\) m = \(-\frac{1}{5}\) Therefore, The slope of the required line is, m = \(\frac{1}{Slope \ of \ joining\ line(2,5) and (-3,6)}\) So, m = \(-\frac{1}{\frac{1}{5}}\) m = 5 Now, The equation of straight line is (y – y1) = m(x – x1) y – 5 = 5 (x – ( – 3) y – 5 = 5x + 15 5x – y + 20 = 0 Hence, The equation of line is 5x – y + 20 = 0 |
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| 103. |
Find the equation of the perpendicular bisector of the line segment joining the points A(2, 3) and B(6, – 5). |
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Answer» The mid-point of A(2, 3) and B(6, – 5), = \((\frac{2+6}{2},\frac{3-5}{2})=(4, -1)\) And slope of AB, m =\(\frac{-5-3}{6-2}=-2\) ∴ Slope of the Perpendicular bisector of AB, m’ = \(\frac{-1}{m}=\frac{1}{2}\). Since the bisector passes through (4, – 1), so the equation of the Perpendicular bisector is Y – (– 1) = \(\frac{1}{2}\)( – 4) ⇒ y + 1 = \(\frac{1}{2}\)(x − 4) ⇒ x – 4 = 2y + 2 ⇒ x – 2y – 6 = 0, is the required equation. |
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| 104. |
A(2, 4) and B(5, 8), find the equation of the locus of point P such that PA2 – PB2 = 13. |
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Answer» Let P(x, y) be any point on the required locus. Given, A(2,4), B(5, 8) and PA2 -PB2 = 13 ∴ [(x -2)2 + (y – 4)2 ] – [(x -5)2 + (y- 8)2] = 13 ∴ (x2 – 4x + 4 + y2 – 8y + 16) – (x2 – 10x + 25 + y2 – 16y + 64) =13 ∴ x2 – 4x+ y2 – 8y + 20 – x2 + 10x – y2 + 16y – 89 = 13 ∴ 6x + 8y- 69 = 13 ∴ 6x + 8y – 82 = 0 ∴ 3x + 4y – 41 = 0 ∴ The required equation of locus is 3x + 4y-41 = 0. |
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| 105. |
A(- 5,2) and B(4,1). Find the equation of the locus of point P, which is equidistant from A and B. |
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Answer» Let P(x, y) be any point on the required locus. P is equidistant from A(- 5, 2) and B(4, 1). ∴ PA = PB ∴ PA2 = PB2 ∴ (x + 5)2 + (y – 2)2 = (x – 4)2 + (y – 1)2 ∴ x2 + 10x + 25 + y2 — 4y + 4 = x2 – 8x + 16 + y2 – 2y + 1 ∴ 10x – 4y + 29 = -8x – 2y + 17 ∴ 18x – 2y + 12 = 0 ∴ 9x – y + 6 = 0 The required equation of locus is 9x -y + 6 = 0. |
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| 106. |
If A(2, 0) and B(0, 3) are two points, find the equation of the locus of point P such that AP = 2BP. |
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Answer» Let P(x, y) be any point on the required locus. Given, A(2, 0), B(0, 3) and AP = 2BP ∴ AP2 = 4BP2 ∴ (x – 2)2 + (y – 0)2 = 4[(x – 0)2 + (y – 3)2] ∴ x2 – 4x + 4 + y2 = 4(x2 + y2 – 6y + 9) x2 – 4x + 4 + y2 = 4x2 + 4y2 – 24y + 36 ∴ 3x2 + 3 y2 + 4x – 24y + 32 = 0 ∴ The required equation of locus is 3x2 + 3y2 + 4x – 24y + 32 = 0. |
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| 107. |
Find equation of the line perpendicular to the line x – 7y + 5 = 0 and having x intercept 3. |
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Answer» The given equation of line is x – 7y + 5 = 0. or, y = 1/7 X + 5/7 which is of the form y = mx + c ∴Slope of the given line = 1/7 The slope of the line perpendicular to the line having a slope of 1/7 is m = - 1/(1/7) = -7 The equation of the line with slope –7 and x-intercept 3 is given by y = m (x – d) ⇒ y = –7 (x – 3) ⇒ y = –7x + 21 ⇒ 7x + y = 21 |
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| 108. |
Find the equation to the straight line which cuts off equal positive intercepts on the axes and their product is 25 |
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Answer» Concept Used: The equation of the line with intercepts a and b is \(\frac{x}{a}+\frac{y}{b}=1\) To find: The equation of the line which cutoff intercepts on the axes. Given: Here a = b and ab = 25 Explanation: ∴ a2 = 25 ⇒ a = 5 since we are to take only positive value of intercepts Hence, the equation of the required line is Formula used: \(\frac{x}{a}+\frac{y}{b}=1\) \(\frac{x}{5}+\frac{y}{5}=1\) ⇒ x + y = 5 Hence, the equation of line is x + y = 5 |
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| 109. |
Find the equation of the line having inclination 135° and making x-intercept 7. |
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Answer» Given, Inclination of line = 0 = 135° ∴ Slope of the line (m) = tan 0 = tan 135° = tan (90° + 45°) = – cot 45° = – 1 x-intercept of the required line is 7. ∴ The line passes through (7, 0). Equation of the line in slope point form is y1 – y = m(x – x1) ∴ The equation of the required line is y — 0 = – 1 (x – 7) ∴ y = -x + 7 ∴ x + y – 7 = 0 y= aX+b:-->, where a is the slope of the line and b, is the y-intercept.when x takes a value of 0 then aX = 0 and then y =b (that's why b is the y-intercept ). Accordingly, calculate the slope which is tan(theta) ( sin(theta)/cos(theta)= y/x) put that value to be the (a) in the equation, and put the y-intercept (+7) in place of b final eq--> y= tan(135)X+7 |
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| 110. |
The angle between the lines 2x – y + 3 = 0 and x + 2y + 3 = 0 is A. 90° B. 60° C. 45° D. 30° |
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Answer» Let m1 and m2 be the slope of the lines 2x − y + 3 = 0 and x + 2y + 3 = 0, respectively. Let θ be the angle between them. Here, m1 = 2 and m2 = \(-\frac{1}{2}\) ∵ m1m2 = − 1 Therefore, the angle between the given lines is 90°. |
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| 111. |
Find the angles between each of the following pairs of straight lines : 3x + 4y – 7 = 0 and 4x – 3y + 5 = 0 |
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Answer» Given: The equations of the lines are 3x + 4y − 7 = 0 … (1) 4x − 3y + 5 = 0 … (2) To find: Angles between two lines. Explanation: Let m1 and m2 be the slopes of these lines. m1 = \(-\frac{3}{4}\) ,m2 = \(\frac{4}{3}\) ∵m1m2 = \(-\frac{3}{4}\times\frac{4}{3}=-1\) Hence, the given lines are perpendicular. Therefore, the angle between them is 90°. |
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| 112. |
Prove that the points (2, -1), (0, 2), (2, 3) and (4, 0) are the coordinates of the vertices of a parallelogram and find the angle between its diagonals. |
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Answer» To prove: The points (2, -1), (0, 2), (2, 3) and (4, 0) are the coordinates of the vertices of a parallelogram Let us assume the points, A (2, − 1), B (0, 2), C (2, 3) and D (4, 0) be the vertices. Now, let us find the slopes Slope of AB = [(2 + 1) / (0 - 2)] = -3/2 Slope of BC = [(3 - 2) / (2 - 0)] = 1/2 Slope of CD = [(0 - 3) / (4 - 2)] = -3/2 Slope of DA = [(-1 - 0) / (2 - 4)] = 1/2 Thus, AB is parallel to CD and BC is parallel to DA. Hence proved, the given points are the vertices of a parallelogram. Now, let us find the angle between the diagonals AC and BD. Let m1 and m2 be the slopes of AC and BD, respectively. m1 = [(3 + 1) / (2 - 2)] = ∞ m2 = [(0 - 2) / (4 - 0)] = -1/2 Thus, the diagonal AC is parallel to the y-axis. ∠ODB = tan-1 (1/2) In triangle MND, ∠DMN = π/2 – tan-1 (1/2) ∴ The angle between the diagonals is π/2 – tan-1 (1/2). |
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| 113. |
Write the equation of the line: Parallel to the X-axis and at a distance of 5 units from it and above it |
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Answer» Equation of a line parallel to X-axis is y = k. Since the line is at a distance of 5 units above the X-axis, k = 5 ∴ The equation of the required line is y = 5. |
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| 114. |
Find the equation of the straight line passing through (–2, 3) and indicated at an angle of 45° with the x – axis. |
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Answer» Given: A line which is passing through (–2, 3), the angle is 45°. By using the formula, Here, angle, θ = 45° The slope of the line, m = tan θ m = tan 45° = 1 The line passing through (x1, y1) = (–2, 3) The required equation of line is y – y1 = m(x – x1) Now, substitute the values, we get y – 3 = 1(x – (– 2)) y – 3 = x + 2 x – y + 5 = 0 ∴The equation of line is x – y + 5 = 0 |
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| 115. |
Find the equation of the line: Passing through the points P(2, 1) and Q(2,-1) |
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Answer» The required line passes through the points P(2, 1) and Q(2,-1). Since both the given points have same x co-ordinates i.e. 2, the given points lie on the line x = 2. ∴ The equation of the required line is x = 2. |
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| 116. |
Write the equation of the line: Parallel to the Y-axis and at a distance of 5 units from it and to the left of it. |
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Answer» Equation of a line parallel to the Y-axis is x = h. Since the line is at a distance of 5 units to the left of the Y-axis, h = -5 ∴ The equation of the required line is x = -5. |
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| 117. |
Find the equation of the straight line passing through ( – 2, 3) and indicated at an angle of 45° with the x – axis. |
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Answer» A line which is passing through ( – 2,3), the angle is 45° . To Find: The equation of a straight line. Formula used: The equation of line is [y – y1 = m(x – x1)] Explanation: Here, angle, θ = 45° SO, The slope of the line, m = tan θ m = tan 45° m = 1 The line passing through (x1,y1) = ( – 2,3) The required equation of line is y – y1 = m(x – x1) y – 3 = 1(x – ( – 2)) y – 3 = x + 2 x – y + 5 = 0 Hence, The equation of line is x – y + 5 = 0 |
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| 118. |
Find the equation of a line parallel to the x - axis at a distance of(i) 4 units above it(ii) 5 units below it |
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Answer» (i) Equation of line parallel to x - axis is given by y = constant, as the y - coordinate of every point on the line parallel to x - axis is 4,i.e. constant. Now the point lies above x - axis means in positive direction of y - axis, So, the equation of line is given as y = 4. (ii) Equation of line parallel to x - axis is given by y = constant, as the y - coordinate of every point on the line parallel to x - axis is - 5 i.e. constant. Now the point lies below x - axis means in negative direction of y - axis, So, the equation of line is given as y = - 5. |
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| 119. |
Find the equation of a line parallel to the y - axis at a distance of(i) 6 units to its right(ii) 3 units to its left |
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Answer» (i) Equation of line parallel to y - axis is given by x = constant, as the x - coordinate of every point on the line parallel to y - axis is 6 i.e. constant. Now the point lies to the right of y - axis means in the positive direction of x - axis, So, required equation of line is x = 6. (ii) Equation of line parallel to y - axis is given by x = constant, as the x - coordinate of every point on the line parallel to y - axis is - 3. Now point lies to the left of y - axis means in the negative direction of x - axis, So, required equation of line is given as x = - 3. |
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| 120. |
Find the slope and the equation of the line passing through the points: (a, b) and (- a, b) |
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Answer» The slope of the equation can be calculated using m = \(\frac{y_2-y_1}{x_2-x_1}\) ⇒ b-b/-a-a = 0 m = 0 (Horizontal line) Now using two point form of the equation of a line y - y1 = \(\frac{y_2-y_1}{x_2-x_1}\)(x - x1) y - b = 0(x - a) y = b So, required equation of line is y = b. |
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| 121. |
Show that the line joining (2, – 3) and (– 5, 1) is parallel to the line joining (7, – 1) and (0, 3). |
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Answer» To Prove: The given line is parallel to another line. Proof: Let Assume the coordinate A(2, – 3) and B(– 5, 1), C(7, – 1) and D(0,3). The concept used: Slopes of the parallel lines are equal. The formula used: The slope of the line, m = \(\frac{y_2-y_1}{x_2-x_1}\) Now, The slope of AB = \(\frac{1-(-3)}{-5-2}\) The Slope of AB = \(\frac{4}{-7}\) Now, The slope of CD = \(\frac{3-(-1)}{0-7}\) The Slope of AB = \(\frac{4}{-7}\) So, The slope of AB = The slope of CD Hence, The given Lines are parallel to each other. |
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| 122. |
Show that the line joining (2, – 5) and (– 2, 5) is perpendicular to the line joining (6, 3) and (1,1). |
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Answer» To Prove: The Given line is perpendicular to each other. Proof: Let Assume the coordinate A(2, – 5) and B(– 2, 5) joining the line AB, C(6,3) and D(1,1) joining the line CD. The concept used: The product of the slopes of lines always – 1. The formula used: The slope of the line, m = \(\frac{y_2-y_1}{x_2-x_1}\) Now, The slope of AB = \(\frac{5-(-5)}{-2-2}\) The Slope of AB = \(\frac{10}{-4}\) Now, The slope of CD = \(\frac{1-3}{1-6}\) The Slope of AB = \(\frac{2}{5}\) So, AB × CD = \(\frac{10}{-4}\times\frac{2}{5}\) AB × CD = – 1 Hence, The given Lines are perpendicular to each other. |
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| 123. |
Obtain the equation of the line which is: Parallel to the X-axis and 3 units below it |
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Answer» Equation of a line parallel to X-axis is y = k. Since the line is at a distance of 3 units below X-axis, k = -3 ∴ The equation of the required line is y = -3. |
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| 124. |
Obtain the equation of the line which is: Parallel to the Y-axis and 2 units to the left of it. |
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Answer» Equation of a line parallel to Y-axis is x = h. Since the line is at a distance of 2 units to the left of Y-axis, h = -2 ∴ The equation of the required line is x = -2 |
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| 125. |
Obtain the equation of the line which is: Parallel to the X-axis and making an intercept of 5 on the Y-axis. |
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Answer» Equation of a line parallel to X-axis with y-intercept ‘k’ is y = k. Here, y-intercept = 5 ∴ The equation of the required line is y = 5. |
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| 126. |
Find the slope of a line which passes through the points(i) (0, 0) and (4, -2)(ii) (0, -3) and (2, 1)(iii) (2, 5) and (-4, -4)(iv) (-2, 3) and (4, -6) |
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Answer» If a line passing through (x1, y1) & (x2, y2) then slope of the line is given by slope = (y2-y1/x2-x1) (i) Given points are (0,0) and (4,-2) slope = (-2-0/4-0) = -1/2 (ii) Given points are (0, -3) and (2, 1) slope = (1-(-3)/2-0) = 2 (iii) Given points are (2, 5) and (-4, -4) slope = (-4-5/-4-2) = 3/2 = 1.5 (iv) Given points are (-2, 3) and (4, -6) slope = (-6-3/4+2) = - 3/2 = -1.5 |
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| 127. |
Find the equation of a line parallel to the x - axis and having intercept - 3 on the y - axis. |
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Answer» Equation of line parallel to x - axis is given by y = constant, as x - coordinate of every point on the line parallel to y - axis is - 3 i.e. constant. So, the required equation of line is y = - 3 |
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| 128. |
Find the equation of the line passing through (0, 0) with slope m |
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Answer» Given, A straight line passing through the point (0,0) and slope is m. To Find: The equation of the straight line. Formula used: The equation of line is [y – y1 = m(x – x1)] Explanation: Here, The line is passing through (0,0) The slope of line, m = m (Given) Coordinates of line are (x1,y1) = (0,0) The equation of line = y – y1 = m(x – x1) By putting the values, we get y – 0 = m(x – 0) y = mx Hence, The equation of line is y = mx. |
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| 129. |
Find the equation of the line: Passing through the points A(2, 0) and B(3,4) |
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Answer» The required line passes through the points A(2, 0) and B(3,4). Equation of the line in two point form is \(\frac {y-y_1}{y_2-y_1}= \frac {x-x_1}{x_2-x_1}\) Here, (x y ) = (2,0) and (x ,y ) = (3,4) ∴ The equation of the required line is ∴ \(\frac {y-0}{4-0}= \frac {x-2}{3-2}\) ∴ y/4 = x-2/1 ∴ y = 4(x – 2) ∴ y = 4x – 8 ∴ 4x – y – 8 = 0 |
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| 130. |
Obtain the equation of the line containing the point: A(2, – 3) and parallel to the Y-axis. |
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Answer» Equation of a line parallel to Y-axis is of the form x = h. Since the line passes through A(2, – 3), h = 2 ∴ The equation of the required line is x = 2. |
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| 131. |
Find the equation of a horizontal line passing through the point (4, - 2). |
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Answer» Equation of line parallel to x - axis (horizontal) is y = constant, as y - coordinate of every point on the line parallel to x - axis is - 2 i.e. constant. Therefore equation of the line parallel to x - axis and passing through (4, - 2) is y = - 2. |
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| 132. |
Find the equation of the line passing through (2, 2√3) and inclined with x – axis at an angle of 75°. |
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Answer» A line which is passing through (2,2√3), the angle is 75°. To Find: The equation of a straight line. Formula used: The equation of line is [y – y1 = m(x – x1)] Explanation: Here, angle, θ = 75° So, The slope of the line, m = tan θ m = tan 75° m = 3.73 = 2 + √3 The line passing through (x1,y1) = (2,2√3) The required equation of the line is y – y1 = m(x – x1) y – 2√3 = 2 + √3 (x – 2) y – 2√3 = (2 + √3)x – 7.46 (2 + √3)x – y – 4 = 0 Hence, The equation of the line is (2 + √3)x – y – 4 = 0 |
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| 133. |
Find a point on the y-axis which is equidistant from A(-4, 3) and B(5, 2). |
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Answer» Let the point on the y-axis be P(0, y) Given: P is equidistant from A(- 4, 3) and B(5, 2). i.e., PA = PB ⇒ \(\sqrt{(-4-0)^2+(3-y)^2}\) = \(\sqrt{(5-0)^2+(2-y)^2}\) Squaring both sides, we get ⇒ (- 4 – 0)2 + (3 – y)2 = (5 – 0)2 + (2 – y)2 ⇒ 16 + 9 – 6y + y2 = 25 + 4 – 4y + y2 ⇒ 25 – 6y = 29 – 4y ⇒ 2y = - 4 ⇒ y = - 2 Therefore, the required point on the y-axis is (0, - 2). |
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| 134. |
Find the equation of the straight line which passes through the point (1,2) and makes such an angle with the positive direction of x – axis whose sine is \(\frac{3}{5}\) . |
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Answer» A line which is passing through (1,2) To Find: The equation of a straight line. Formula used: The equation of line is [y – y1 = m(x – x1)] Explanation: Here, sin θ = \(\frac{3}{5}\) We know, sin θ = \(\frac{perpendicular}{Hypotenues}\) = \(\frac{3}{5}\) According to Pythagoras theorem, (Hypotenuse)2 = (Base)2 + (Perpendicular)2 (5)2 = (Base)2 + (3)2 (Base) = \(\sqrt{25-9}\) (Base)2 = \(\sqrt{16}\) Base = 4 Hence, tan θ = \(\frac{Perpendicular}{Base}\) = \(\frac{3}{4}\) SO, The slope of the line, m = tan θ m = \(\frac{3}{4}\) The line passing through (x1,y1) = (1,2) The required equation of line is y – y1 = m(x – x1) y – 2 = \(\frac{3}{4}\)(x – 1) 4y – 8 = 3x – 3 3x – 4y + 5 = 0 Hence, The equation of line is 3x – 4y + 5 = 0 Answer: Equation of the line = 3x - 4y + 5 = 0 Step-by-step explanation: Given:
To Find:
Solution: Here we have to first find the slope of the line We know that, m = tan θ where m is the slope. We know that sin θ = opposite/hypotenuse = 3/5 Hence by Pythagoras theorem finding the adjacent side, Adjacent side = √(25 - 9) Adjacent side = √16 = 4 units Also, tan θ = opposite/adjacent = 3/4 Hence slope of the line is 3/4. Now point slope form of a line is given by, y - y₀ = m (x - x₀) Here (1,2) = (x₀, y₀) Substitute the data, y - 2 = 3/4 (x - 1) Multiply whole equation by 4 4y - 8 = 3x - 3 3x - 4y + 5 = 0 Hence the equation of the line is 3x - 4y + 5 = 0 |
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| 135. |
Find the equation of a vertical line passing through the point ( - 5, 6). |
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Answer» Equation of line parallel to y - axis (vertical) is given by x = constant, as x - coordinate is constant for every point lying on line i.e. 6. So, the required equation of line is given as x = 6. |
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| 136. |
Find the equation of a line whose slope is 4 and which passes through the point (5, - 7) |
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Answer» As slope is given m = 4 and passing through (5, - 7).using slope - intercept form of equation of line, we will find value of intercept first y = mx + c ………..(1) - 7 = 4(5) + c - 7 = 20 + c c = - 7 - 20 c = - 27 Putting the value of c in equation (1), we have y = 4x + ( - 27) y = 4x - 27 4x - y - 27 = 0 So, the required equation of line is 4x - y - 27 = 0. |
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| 137. |
Find the equation of the parallel to x–axis and passing through (3, –5). |
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Answer» Given: A line which is parallel to x–axis and passing through (3, –5) By using the formula, The equation of line: [y – y1 = m(x – x1)] We know that the parallel lines have equal slopes And, the slope of x–axis is always 0 Then The slope of line, m = 0 Coordinates of line are (x1, y1) = (3, –5) The equation of line = y – y1 = m(x – x1) Now, substitute the values, we get y – (– 5) = 0(x – 3) y + 5 = 0 ∴ The equation of line is y + 5 = 0 |
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| 138. |
Find the equation of the line perpendicular to x–axis and having intercept – 2 on x–axis. |
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Answer» Given: A line which is perpendicular to x–axis and having intercept –2 By using the formula, The equation of line: [y – y1 = m(x – x1)] We know that, the line is perpendicular to the x–axis, then x is 0 and y is –1. The slope of line is, m = y/x = -1/0 It is given that x–intercept is –2, so, y is 0. Coordinates of line are (x1, y1) = (–2, 0) The equation of line = y – y1 = m(x – x1) Now, substitute the values, we get y – 0 = (-1/0) (x – (– 2)) x + 2 = 0 ∴ The equation of line is x + 2 = 0 |
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| 139. |
Find the equation of the line parallel to x–axis and having intercept – 2 on y – axis. |
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Answer» Given: A line which is parallel to x–axis and having intercept –2 on y – axis By using the formula, The equation of line: [y – y1 = m(x – x1)] The parallel lines have equal slopes, And, the slope of x–axis is always 0 Then The slope of line, m = 0 It is given that intercept is –2, on y – axis then Coordinates of line are (x1, y1) = (0, – 2) The equation of line is y – y1 = m(x – x1) Now, substitute the values, we get y – (– 2) = 0 (x – 0) y + 2 = 0 ∴ The equation of line is y + 2 = 0 |
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| 140. |
The equation of the line passing through the point (1,2) and perpendicular to the line x + y + 1 = 0 is(A) y – x + 1 = 0 (B) y – x – 1 = 0(C) y – x + 2 = 0 (D) y – x – 2 = 0 |
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Answer» Answer is (B) Slope of the given line +1=0 is-1. So, slope of line perpendicular to above line is 1. Line passes through the point (1,2). Therefore, equation of the required linens: y-2 = 1(x- 1) => y-x-1=0. |
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| 141. |
The equation of the straight line passing through the point (3, 2) and perpendicular to the line y = x is(A) x – y = 5 (B) x + y = 5(C) x + y = 1 (D) x – y = 1 |
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Answer» Answer is (B) Slope of the given line y = x is 1. Thus, slope of line perpendicular to y = x is -1. Line passes through the point (3, 2). So, equation of the required line is:y-2=-l (x – 3) => x + y = 5 |
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| 142. |
Find the equation of a line for which p = 8, α = 300° |
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Answer» Given: p = 8, α = 300° Concept Used: Equation of line in normal form. Explanation: So, the equation of the line in normal form is Formula Used: x cos α + y sin α = p x cos 300° + y sin 300° = 8 ⇒ x cos (360° – 60°) + y sin (360° – 60°) = 8 We know, cos (360° – θ) = cos θ, sin (360° – θ) = – sin θ ⇒ x cos60° – y sin60° = 8 ⇒ \(\frac{x}{2}-\frac{\sqrt{3}y}{2}\) ⇒ x – √3y = 16 Hence, the equation of line in normal form is x – √3y = 16 |
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| 143. |
Fill in the blanks:If a, b, c are in A.P., then the straight lines ax + by + c = 0 will always pass through ____. |
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Answer» Given: a, b, c are in AP b = (a + c)/2 ⇒ 2b = a + c ⇒ a – 2b + c = 0 …(i) Now, comparing the eq. (i) with the given equation ax + by + c = 0, we get x = 1, y = -2 So, the line will pass through (1, -2) Ans. If a, b, c are in A.P., then the straight lines ax + by + c = 0 will always pass through (1, -2). |
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| 144. |
Prove that the area of the parallelogram formed by the lines 3x – 4y + a = 0, 3x – 4y + 3a = 0, 4x – 3y – a = 0 and 4x – 3y – 2a = 0 is \(\frac{2a^2}{7}\) sq. units. |
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Answer» Given: The given lines are 3x − 4y + a = 0 … (1) 3x − 4y + 3a = 0 … (2) 4x − 3y − a = 0 … (3) 4x − 3y − 2a = 0 … (4) To prove: The area of the parallelogram formed by the lines 3x – 4y + a = 0, 3x – 4y + 3a = 0, 4x – 3y – a = 0 and 4x – 3y – 2a = 0 is \(\frac{2a^2}{7}\) sq. units. Explanation: From Above solution, We know that Area of the parallelogram = \(\Big|\frac{(c_1-d_1)(c_2-d_2)}{\sqrt{a_1b_2-a_2-b_1}}\Big|\) ⇒ Area of the parallelogram = \(\Big|\frac{(a-3a)(2a-a)}{\sqrt{-9+16}}\Big|\) = \(\frac{2a^2}{7}\) square units Hence proved. |
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| 145. |
Find the value of p so that the three lines 3x + y – 2 = 0, px + 2y – 3 = 0 and 2x – y – 3 = 0 may intersect at one point . |
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Answer» The equations of the given lines are |
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| 146. |
Find the value of p so that the three lines 3x + y – 2 = 0, px + 2y – 3 = 0 and 2x – y – 3 = 0 may intersect at one point |
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Answer» The equations of the given lines are |
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| 147. |
Prove that the lines 2x – 3y + 1 = 0, x + y = 3, 2x – 3y = 2 and x + y = 4 form a parallelogram. |
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Answer» Given: 2x – 3y + 1 = 0, x + y = 3, 2x – 3y = 2 x + y = 4 are given equation To prove: The lines 2x – 3y + 1 = 0, x + y = 3, 2x – 3y = 2 and x + y = 4 form a parallelogram. Explanation: The given lines can be written as y = \(\frac{2}{3}\)x + \(\frac{1}{3}\) ..... (1) y = - x + 3 .....(2) y = \(\frac{2}{3}\) x - \(\frac{2}{3}\) ...(3) y = - x + 4 ... (4) The slope of lines (1) and (3) is \(\frac{2}{3}\) and that of lines (2) and (4) is − 1. Thus, lines (1) and (3), and (2) and (4) are two pair of parallel lines. If both pair of opposite sides are parallel then, we can say that it is a parallelogram. Hence proved, the given lines form a parallelogram. |
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| 148. |
Find the equation of the line perpendicular to the line x – 7y + 5 = 0 and having x-intercept 3. |
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Answer» Given line is x-7y + 5 = 0 Slope = m = - a/b = -(1/-7) = 1/7 Slope of the line perpendicular to the given line = – 7 (∵ m1 x m2 =-1) Since x-intercept is 3 then (3, 0) is the point on the required line. ∴ Required equation the line passing through (3, 0) having slope – 7 is, y – 0 = -7(x - 3) i.e., 7x ± y – 21 = 0 |
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| 149. |
Find the equation to the straight line parallel to 3x – 4y + 6 = 0 and passing through the middle point of the join of points (2, 3) and (4, -1). |
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Answer» Given: equation parallel to 3x – 4y + 6 = 0 and passing through the middle point of the join of points (2, 3) and (4, -1). To find: The equation to the straight line parallel to 3x – 4y + 6 = 0 and passing through the middle point of the join of points (2, 3) and (4, -1). Explanation: Let the Given points be A (2, 3) and B (4, − 1). Let M be the midpoint of AB. ∴ Coordinates of M = \(\Big(\frac{2+4}{2},\frac{3-1}{2}\Big)\) = (3,1) The equation of the line parallel to 3x − 4y + 6 = 0 is 3x – 4y + λ = 0 This line passes through M (3, 1). ∴ 9 – 4 + λ = 0 ⇒ λ = -5 Substituting the value of λ in 3x – 4y + λ = 0, we get 3x – 4y – 5 = 0 Hence, the equation of the required line is 3x – 4y – 5 = 0. |
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| 150. |
Find the equation of a line passing through the point (2, 3) and parallel to the line 3x– 4y + 5 = 0. |
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Answer» Given: equation is parallel to 3x − 4y + 5 = 0 and pass through (2, 3) To find: Equation of required line. Explanation: The equation of the line parallel to 3x − 4y + 5 = 0 is 3x – 4y + λ = 0, Where, λ is a constant. It passes through (2, 3). ∴6 – 12 + λ = 0 ⇒ λ = 6 Hence, the required line is 3x − 4y + 6 = 0. |
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