Question

resolva o sistemas : 3x+y=-6x(-3) 3x+3y=-18 ​

Answer 1

$\Large\boxed{\begin{array}{l}\begin{cases}\sf 3x+y=-6\\\sf 3x+3y=18\end{cases}\\\\\begin{cases}\sf3x+y=-6\cdot(-1)\\\sf3x+3y=18\end{cases}\\\\+\underline{\begin{cases}\sf -\diagdown\!\!\!\!\!\!3x-y=6\\\sf\diagdown\!\!\!\!\!\!3x+3y=18\end{cases}}\\\sf 2y=24\\\sf y=\dfrac{24}{2}\\\\\sf y=12 \\\sf 3x+y=-6\\\sf 3x+12=-6\\\sf 3x=-12-6\\\sf 3x=-18\\\sf x=-\dfrac{18}{3}\\\\\sf x=-6\\\sf S=\{-6,12\}\end{array}}$