Answer:
2x^2 + 2y^2
Step-by-step explanation:
Combine like terms.
(x^2 + 2xy + y^2) + (x^2 - 2xy + y^2) =
= x^2 + 2xy + y^2 + x^2 - 2xy + y^2
= x^2 + x^2 + 2xy - 2xy + y^2 + y^2
= 2x^2 + 2y^2
