Question

d) { x + y = 30 x - y = 80​

Answer 1

$\LARGE\displaystyle{}\begin{cases}x + y = 30 \\ \\ x - y = 80\end{cases} \\\\ \LARGE\displaystyle{}\begin{cases}x + y = 30 \\ \\ x = 80 + y\end{cases} \\\\ \LARGE\displaystyle{}80 + y + y = 30 \\\LARGE\displaystyle{}y = - 25 \\\\ \LARGE\displaystyle{}x = 80 + \left( - 25\right) \\ \\ \LARGE\displaystyle{}x = 55 \\ \\ \LARGE\displaystyle\text{ \begin{gathered} \underline{\boxed{\boldsymbol{ \left(x,y\right) =\left(55, - 25\right) }}}\end{gathered} }$

$\LARGE\displaystyle\text{ \begin{gathered} \underline{\boxed{\boldsymbol{{ \red{Bons}} \blue{\:Estudos}}}}\end{gathered} }$