Let R be a rectangle given by the lines x=0,x=2, y=0 and y=5. Let A(α,0) and B(0,β),α∈[0,2] and β∈[0,5], be such that the line segment AB divides the area of the rectangle R in the ratio 4:1. Then, the mid-point of AB lies on a
(A)parabola
(B)hyperbola✓ Correct
(C)straight line
(D)circle
Answer: (B)
Solution
The rectangle has area 10. The line AB divides it in ratio 4:1, so the triangle OAB has area 2 (since the larger region has area 8). The area of triangle OAB is 21αβ=2, giving αβ=4. Let the midpoint M be (h,k)=(α/2,β/2). Then α=2h and β=2k, so (2h)(2k)=4, which gives hk=1. The locus is xy=1, which is a hyperbola.
JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Single correct option