Let the line L intersect the lines x - 2 = -y = z - 1, 2(x + 1) = 2(y - 1) = z + 1 and be parallel to the line x - 23 = y - 11 = z - 22. Then which of the following points lies on L ?
- (- 13, 1, -1 )
- (- 13, -1, 1 )
- (- 13, -1, -1 )
- (- 13, 1, 1 )
Answer
(1) (- 13, 1, -1 )
Solution
Point on the first line: M( + 2, - , + 1)
Second line is x + 1 = y - 1 = z + 12, so a point on it is N( - 1, + 1, 2 - 1).
L = MN is parallel to (3, 1, 2), so the d.r.'s of MN, ( - + 3, - - - 1, - 2 + 2), are proportional to 3 : 1 : 2:
- + 3 = 3(- - - 1) 2 + = -3
- 2 + 2 = 2(- - - 1) = - 43, hence = - 13
So M ( 23, 43, - 13 ) and L: x - 233 = y - 431 = z + 132 = t
For x = - 13: t = - 13, which gives y = 1, z = -1, i.e. the point (- 13, 1, -1 ).
Answer: (1)