A line with direction ratios 1, -1, 2 intersects the lines x2= y3= z+13 and x+1-1= y-21= z4 at the points P and Q, respectively. If the length of the line segment PQ is , then 225 2 is equal to:
- 1024
- 1014
- 1104
- 1204
Answer
(2) 1014
Solution
Take P = (2s, 3s, 3s - 1) on the first line and Q = (-1 - t, 2 + t, 4t) on the second. Since PQ has direction ratios 1, -1, 2,
PQ = (-1 - t - 2s, 2 + t - 3s, 4t - 3s + 1) = (1, -1, 2)
Adding the first two components gives 1 - 5s = 0, so s = 15 and = -1 - t - 25 = - 75 - t.
The third component then gives
4t - 35 + 1 = 2 (- 75 - t ) 6t = - 165 t = - 815
= - 75 + 815 = - 1315
Hence = PQ = | | 1 + 1 + 4 = 13 615
∴ 225 2 = 169 6 = 1014
Answer: (2)