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Options

A. 3
B. 6
C. 8
D. 4

Answer

D

Explanation

The image of a point `(x_(1), y_(1))` in the line mirror `ax+by+c=0` is the point (x, y) given by
`(x-x_(1))/a=(y-y_(1))/b=(2(ax_(1)+by_(1)+c))/(a^(2)+b^(2))`
The image of O(0, 0), P(1, 2) and Q(1, -2) in the line mirror x+y+4=0 are O'(-4, -4), A(-4, -5), and B(-2, -5) respectively. Thus, y = -5 is the image of the latusretum PQ in the lien mirror x+y+4=0.
Hence, AB=PQ=4