Question

Find the equation of latus rectum of parabola y^2=-100x.

(a) x=25

(b) x=-25

(c) y=-25

(d) y=25

The question was posed to me in an internship interview.

This intriguing question comes from Conic Sections topic in division Conic Sections of Mathematics – Class 11

Answer 1

Right choice is (b) x=-25

To explain I would say: Comparing equation with y^2=-4ax.

4a=100 => a=25. Line passing through focus perpendicular to axis is latus rectum.

Equation of latus rectum is x=-a => x=-25.