Question

The equation of directrix of the parabola y² = -x is: 

(a) 4x + 1 = 0 

(b) 4x – 1 = 0 

(c) x – 1 = 0 

(d) x + 4 = 0

Answer 1

(b) 4x – 1 = 0

y² = -x. 

It is a parabola open leftwards. 

Here 4a = 1 ⇒ a = \(\frac{1}{4}\)

Equation of directrix is x = a. 

i.e., x = \(\frac{1}{4}\) (or) 4x – 1 = 0