Let ( , , ) be the image of the point (8, 5, 7) in the line x - 12 = y + 13 = z - 25. Then + + is equal to :
- 16
- 20
- 18
- 14
Answer
(4) 14
Solution
Foot of perpendicular from P(8, 5, 7): M(2 + 1, 3 - 1, 5 + 2)
PM line: 2(2 - 7) + 3(3 - 6) + 5(5 - 5) = 0
38 = 57 = 32 M (4, 72, 192 )
M is the mid-point of P and its image image = 2M - P = (8 - 8, 7 - 5, 19 - 7) = (0, 2, 12)
+ + = 0 + 2 + 12 = 14
Answer: (4)