Explanation:
If x = 2 and x = -4 are roots of the equation, then x-2 = 0 and x+4 = 0 are both true after we get everything to one side. This leaves 0 on the other side.
Use the zero product property to end up with (x-2)(x+4)
Then FOIL that out to get x^2+4x-2x-8 = x^2+2x-8
