First, MAY be the same as , depending on what you are doing. Be more careful.

Second, my rule, ALWAYS do it both ways so that you gain experience and you can check your own answer.

Washers: Substitute for 'x' and evaluate. With consideration for symmetry, this could be

Cyllinders: . Substitute for 'y' and evaluate. The 2y is there ONLY because of symmetry, otherwise, it would have been uglier.