Question

The length of latus rectum of the parabola x – 4x – 8y + 12 = 0 is ________ 

(A) 4 

(B) 6 

(C) 8 

(D) 10

Answer 1

Correct option is: (C) 8

Given equation of parabola is 

x² – 4x – 8y + 12 = 0 

⇒ x² – 4x = 8y – 12 

⇒ x² – 4x + 4 = 8y – 12 + 4 

⇒ (x – 2)² = 8(y – 1) 

Comparing this equation with (x – h)² = 4b(y – k), we get

4b = 8 

∴ Length of latus rectum = 4b = 8