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If `y= 3x+c` is a tangent to the circle `x^2+y^2-2x-4y-5=0` , then `c` is equal to :A. `(-2, 3)`B. `(4, -1)`C. `(2, -3)`D. `(4, 1)` |
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Answer» Correct Answer - A::D Equation of given circle `x^(2) + y^(2) - 2x - 4y - 5 = 0` `rArr (x-1)^(2) + (y - 2)^(2) = 0` Equation of tangent `y = 3x + c` Length of the perpendicular from centre `=` radius `|(3-2+c)/(sqrt(3^(2)+1^(2)))| = sqrt(10) rArr c = 9.-11` If `c = 9` then point of contact is `(-2,3)` if `c = -11` then point of contact is `(4, 1)` |
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