A line passes through the origin and makes equal angles with the positive coordinate axes. It intersects the lines L1: 2x+y+6=0 and L2: 4x+2y-p=0, p>0, at the points A and B, respectively. If AB = 9 2 and the foot of the perpendicular from the point A on the line L2 is M, then AMBM is equal to
- 5
- 3
- 2
- 4
Answer
(2) 3
Solution
The line through O making equal angles with the axes is y = x.
With L1: 2x + x + 6 = 0 x = -2
A = (-2, -2)
With L2: 6x = p B = ( p6, p6 )
AB = 2 | p6 + 2 | = 9 2
p6 + 2 = 92 (as p > 0)
p = 15, L2: 4x + 2y - 15 = 0
AM = distance of A from L2
= |-8 - 4 - 15| 16+4 = 272 5
In right AMB (right angle at M):
BM2 = AB2 - AM2 = 812 - 72920 = 8120
BM = 92 5
AMBM = 279 = 3
Answer: (2)