Let P( , , ) be the image of the point Q(1, 6, 4) in the line x1 = y - 12 = z - 23. Then 2 + + is equal to
Answer
11
Solution
Foot of perpendicular on the line: R(t, 2t + 1, 3t + 2)
[figure]
QR = (t - 1, 2t - 5, 3t - 2) (1, 2, 3)
(t - 1) + 2(2t - 5) + 3(3t - 2) = 0 14t = 17
∵ R is the mid-point of PQ: P = 2R - Q
= 2t - 1, = 4t - 4, = 6t
∴ 2 + + = 14t - 6 = 17 - 6 = 11
Answer: 11