x=11 Write the standard form of the equation of the parabola with the given directrix and vertex at (0,0)

We are asked to write the equation of the parabola with vertex at the origin and directrix x=11:
The equation of a parabola with vertex at the origin and focus at (a,0) is y^2=4ax ; the parabola opens to the right if a>0 and to the left if a<0.
The vertex is the midpoint of the perpendicular segment drawn from the focus to the directrix.
Here the focus will be at (-11,0) so the equation we seek is y^2=-44x