Vertex A(0,0); focus S(−2,0)
Since, the vertex of the parabola is 0,0)and the focus lies on the negative x-axis . So, x-axis is the axis of the parabola .
Equation of the parabola is of the form y2=−4ax
Since, the focus is (−2,0). So, a=2
Thus, the equation of the parabola is y2=−8x