# What is the equation of a parabola, whose vertex is (0,0) and directrix is x=-3?

Equation of parabola is ${y}^{2} = 12 x$
As directrix is $x = - 3$ and vertex is $\left(0 , 0\right)$, the equation is of type ${y}^{2} = 4 a x$
In such an equation of parabola, directrix is $x = - a$. Hence $a = 3$ and equation of parabola is ${y}^{2} = 12 x$