Solve the System by the Elimination Method or a Combination $\begin{aligned} x^{2}+2 x y+y^{2} & =9 \\ x^{2}+2 x y-y^{2} & =-9\end{aligned}$

Multiple Choice

Solve the system by the elimination method or a combination of the elimination and substitution methods.
- $\begin{aligned} x^{2}+2 x y+y^{2} & =9 \\ x^{2}+2 x y-y^{2} & =-9\end{aligned}$

A) $\{(0,3) ,(0,-3) ,(-6,3) ,(6,-3) \}$
B) $\{(0,3) ,(0,-3) ,(6,3) ,(6,-3) \}$
C) $\{(0,3) ,(0,-3) ,(-6,3) ,(-6,-3) \}$
D) $\{(0,3) ,(0,-3) ,(6,3) ,(-6,-3) \}$