Question

A parabola is given in its standard form as $y^2=8x$. Equation of the directrix is

• A. $y=-2$
• B. $x=2$
• C. $x=-2$
• D. $y=2$

Answer 1

The correct option is C $x=-2$

the given parabola is $y^2=8x$ ......(1)

the general eqaution of parabola is $y^2=4ax$ ......(2)

by comparing eqn (1) and (2) we get,

$\Rightarrow a=2$, as we know the directrix is,

$\Rightarrow x=-a$ substitute the $a$ value

we get, $\Rightarrow x=-2$.