Hello,

(1. the x-value of the vertex must be the mean of -1 and 5, that means 2, because the first two points have the same y-value, they are situated symmetrical to the axis)

plug in the x- and y-values into the given equation:

This is a system of simultaneous equations. I don't know which method you use. But the solution is: d = -4, E = 1, F = -5

Thus the equation of the parabola is:

EB