Aparabola with a vertex at (0,0) has a focus along the negative part of the x-axis.

which could be the equation of the parabola?

y2 = x
y2 = –2x
x2 = 4y
x2 = –6y

All of them have vertices on (0,0)
for the focus to be on negative part of x axis, make sure that it opens left
so it has to be the y term that is squared
so it is the 1st or 2nd
the first one will give us a parbola opening right
2nd will give us onpening left

answer is y^2=-2x