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The point on y-axis which is at a distance 5 unit from the point (-5, 7) is ___________(a) (7, 0)(b) (0, 7)(c) (1, 7)(d) (7, 7)I had been asked this question during an online exam.My enquiry is from Geometry topic in chapter Coordinate Geometry of Mathematics – Class 10 |
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Answer» RIGHT choice is (B) (0, 7) Easiest explanation: Let the point on y-axis be (0, y) Distance between (-5, 7) and (0, y) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \) = \( \sqrt {(0 + 5)^2 + (y-7)^2} \) = \( \sqrt {y^2-14y + 49 + 25} \) = \( \sqrt {y^2-14y + 74} \) The distance between (-5, 7) and (0, y) is 5 ∴ \( \sqrt {y^2-14y + 74} \) = 5 Squaring on both sides, we get, y^2 – 14y + 74 = 25 y^2 – 14y + 49 = 0 y = 7, 7 Hence, the point is (0, 7) |
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