To check the solutions to any "solving" exercise, plug them back into the original problem. If they work, then this suggests that they are correct.
You appear to have posted two different equations:
. . . . .y(y - 4) = 0
. . . . .(y - 2)(y + 2) = 0
Your solutions will work in one of the equations, but not in the other. Are you requesting assistance with the other...?
Thank you.
Eliz.