Solve the system of equations using substitution.
-$$\left\{ \begin{array} { c }
x y = 72 \
x + y = 17
\end{array} \right.$$
A) $x = 9 , y = 8 ; x = 8 , y = 9$
B) $x = 9 , y = - 8 ; x = 8 , y = - 9$
C) $x = - 9 , y = - 8 ; x = - 8 , y = - 9$
D) $x = - 9 , y = 8 ; x = - 8 , y = 9$

Question

Solve the system of equations using substitution.
-$$\left\{ \begin{array} { c } 
x y = 72 \
x + y = 17
\end{array} \right.$$
A) $x = 9 , y = 8 ; x = 8 , y = 9$
B) $x = 9 , y = - 8 ; x = 8 , y = - 9$
C) $x = - 9 , y = - 8 ; x = - 8 , y = - 9$
D) $x = - 9 , y = 8 ; x = - 8 , y = 9$

Quizplus · Accepted Answer

From the second equation, $y = 17 - x$. Substituting this into the first equation gives $x(17 - x) = 72$, which simplifies to $x^2 - 17x + 72 = 0$. Factoring this equation gives $(x - 9)(x - 8) = 0$, leading to $x = 9$ or $x = 8$. Substituting these values back into $y = 17 - x$ gives the pairs $x = 9, y = 8$ and $x = 8, y = 9$.

Solve the System of Equations Using Substitution {xy=72x+y=17\left\{ \begin{array} { c } x y = 72 \\x + y = 17\end{array} \right.{xy=72x+y=17​

Solve the System of Equations Using Substitution $\left\{ \begin{array} { c } x y = 72 \\x + y = 17\end{array} \right.$