Question

The midpoints of the chords of the parabola y² = 8x which subtend right angle at the vertex lie on the curve y² = kx, where k is equal to

(A)  1

(B)  2

(C)  1/2

(D)  4

Answer 1

Correct option (d)

Explanation :

According to Problem 18 of the section ‘Subjective Problems’, the midpoints lie on a parabola whose latus rectum is half of the latus rectum of the original parabola. Here, the latus rectum of the original parabola is 8 and hence the latus rectum of the required parabola is 4.