Question

como resolvo?
x+2y=5
2x+y=-2​

Answer 1

$\Large\boxed{\begin{array}{l}\begin{cases}\sf x+2y=5\\\sf 2x+y=-2\end{cases}\\\underline{\rm multiplique\,a\,2^a\,equac_{\!\!,}\tilde ao\,por-2:}\\\begin{cases}\sf x+2y=5\\\sf-4x-2y=4\end{cases}\\\underline{\rm adicione\,as\,equac_{\!\!,}\tilde oes\,membro\,a\,membro:}\\+\underline{\begin{cases}\sf x+\diagdown\!\!\!\!\!\!2y=5\\\sf-4x-\diagdown\!\!\!\!\!2y=4\end{cases}}\\\sf -3x=9\cdot(-1)\\\sf 3x=-9\\\sf x=-\dfrac{9}{3}\\\\\sf x=-3\\\sf 2x+y=-2\\\sf 2\cdot(-3)+y=-2\\\sf -6+y=-2\\\sf y=6-2\\\sf y=4\\\sf S=\{-3,4\}\end{array}}$