# How do you solve by substitution x+y=0 and ?

Jun 23, 2015

Substitute $\left(- x\right)$ for each occurrence of $y$ in whatever equation is supplied by "?"; simplify to find the value of $x$; then, equate $y$ to the value of $\left(- x\right)$.
If $x + y = 0$
$\textcolor{w h i t e}{\text{XXXX}}$$y = - x$