Find the standard form of the equation of a parabola (centered at the origin) with a focus at (-5/4, 0) and a vertex at (0, 0).

The axis of the parabola is horizontal, passing through (-5/4,
0) and (0, 0). The standard form when the parabola is centered at the origin is
y^{2}=4px, where h=0, k=0, and p= -5/4.

So the equation is

y^{2}=4(-5/4)x=-5x