If a straight line drawn through the point of intersection of the lines 4x+3y-1=0 and 3x+4y-1=0, meets the co-ordinate axes at the points P and Q, then the locus of the mid point of PQ is :
- x+y-7=0
- x+y-14xy=0
- 2x+y+14xy=0
- x+2y-14xy=0
Answer
(2) x+y-14xy=0
Solution
[figure]
4x+3y=1, 3x+4y=1: subtracting, x=y 7x=1 I ( 17, 17 )
Let M(h, k) be the mid point of PQ P(2h, 0), Q(0, 2k)
Line PQ: x2h+ y2k=1
I lies on PQ: 114h+ 114k=1
h+k=14hk
locus of M: x+y-14xy=0
Answer: (2)