Consider the lines x(3 + 1) + y(7 + 2) = 17 + 5, being a parameter, all passing through a point P. One of these lines (say L) is farthest from the origin. If the distance of L from the point (3, 6) is d, then the value of d2 is
- 10
- 20
- 15
- 30
Answer
(2) 20
Solution
(x + 2y - 5) + (3x + 7y - 17) = 0
All lines pass through the intersection of x + 2y = 5 and 3x + 7y = 17:
y = 2, x = 1
P(1, 2)
The line through P farthest from the origin is perpendicular to OP.
Slope of OP = 2
slope of L = - 12
L: y - 2 = - 12(x - 1) x + 2y - 5 = 0 (member with = 0)
d = |3 + 12 - 5| 1 + 4 = 10 5 = 2 5
d2 = 20
Answer: (2)