1.

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»

(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



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