Since it passes though (-4,-6), then it opens either left or downward, but since it is parallel to the x-axis, then it opens to the left. The equation of the parabola that opens to the left with vertex at the origin is:
y²=4ax
You are given the coordinates, use the coordinates to find a by substituting.
(-6)²=-4a(-4)
36=16a
a=9/2
Substitute the value of a in the equation.
y²=4(9/2)x
y²=18x
The equation of the parabola is y²=18x. Hope this helps =)
