Question

Resolva pelo método de substituição
X+7y=2
-X-4y=-1

Answer 1

$\begin{cases}x+7y=2\\ -x-4y=-1\end{cases}\\\\\\~~ x+7y=2\to~~ x=-7y+2\\\\\\-x-4y=-1\to~~-(-7y+2)-4y=-1\to~~7y-2-4y=-1\to\\\\ 7y-4y=-1+2\to~~ 3y=1\to~~\boxed{y= \frac{1}{3}} \\\\\\ x=-7y+2\to~~ x=-7. \dfrac{1}{3}+2\to~~ x=- \dfrac{7}{3}+2\to~~x= \dfrac{-7+6}{3}\to\\\\ \boxed{x=-\dfrac{1}{3}}\\\\\\\\\\ \large\boxed{\boxed{S=\left\{-\dfrac{1}{3}~;~\dfrac{1}{3} \right\}}}$