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Let P(x1,y1) be a point and let ax + by ...

Let `P(x_1,y_1)` be a point and let ax + by +c =0 be a line. If L (h, k) is the foot of perpendicular drawn from P on this line and `Q (alpha, beta)` is the image of P in the given line, then prove that : `(h-x_1)/a=(k-y_1)/b=-((ax_1+by_1+c)/(a^2+b^2))` .

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