Solve the System by the Substitution Method $$\begin{array} { l } x y = 42 \\x ^ { 2 } + y ^ { 2 } = 85\end{array}$$

Multiple Choice

Solve the system by the substitution method.
- $$\begin{array} { l } x y = 42 \\x ^ { 2 } + y ^ { 2 } = 85\end{array}$$

A) $\{ ( 6,7 ) , ( - 6 , - 7 ) , ( 7,6 ) , ( - 7 , - 6 ) \}$
B) $\{ ( - 6 , - 7 ) , ( - 7 , - 6 ) , ( - 6,7 ) , ( - 7,6 ) \}$
C) $\{ ( 6,7 ) , ( 7,6 ) , ( 6 , - 7 ) , ( 7 , - 6 ) \}$
D) $\{ ( 6,7 ) , ( - 6 , - 7 ) , ( 6 , - 7 ) , ( - 6,7 ) \}$