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Mathematics

Find the point on the x-axis which is equidistant from the points (2, -5) and (-2, 9).

Coordinate Geometry

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Answer

We know that,

y-coordinate of any point on x-axis = 0.

By distance formula,

d = (x2x1)2+(y2y1)2\sqrt{(x2 - x1)^2 + (y2 - y1)^2}

Let point on x-axis which is equidistant from the points (2, -5) and (-2, 9) be P(x, 0).

∴ Distance between (2, -5) and (x, 0) = Distance between (-2, 9) and (x, 0).

(x2)2+[0(5)]2=[x(2)]2+(09)2x2+44x+52=(x+2)2+(9)2x24x+25+4=x2+4+4x+81\Rightarrow \sqrt{(x - 2)^2 + [0 - (-5)]^2} = \sqrt{[x - (-2)]^2 + (0 - 9)^2} \\[1em] \Rightarrow \sqrt{x^2 + 4 - 4x + 5^2} = \sqrt{(x + 2)^2 + (-9)^2} \\[1em] \Rightarrow \sqrt{x^2 - 4x + 25 + 4} = \sqrt{x^2 + 4 + 4x + 81} \\[1em]

On squaring both sides,

x24x+29=x2+4x+85x2x2+4x+4x=29858x=56x=7.\Rightarrow x^2 - 4x + 29 = x^2 + 4x + 85 \\[1em] \Rightarrow x^2 - x^2 + 4x + 4x = 29 - 85 \\[1em] \Rightarrow 8x = -56 \\[1em] \Rightarrow x = -7.

P = (x, 0) = (-7, 0).

Hence, required point is (-7, 0).

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