Question

4 x + y = 7 x - 5y = 9 resultado​

Answer 1

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$\begin{cases}\sf 4x+y=7\\\sf x-5y=9\end{cases}\\\underline{\rm multiplicando~a~1^{\underline a}~equac_{\!\!,}\tilde ao~por~5~temos:}\\+\underline{\begin{cases}\sf20x+\diagdown\!\!\!\!\!5y=35\\\sf x-\diagdown\!\!\!\!\!5y=9\end{cases}}\\\sf21x=44\\\sf x=\dfrac{44}{21}\\\sf 4x+y=7\longrightarrow y=7-4x\\\sf y=7-4\cdot\dfrac{44}{21}\\\sf y=\dfrac{147-176}{21}\\\sf y=-\dfrac{29}{21}\\\huge\boxed{\boxed{\boxed{\boxed{\sf S=\bigg\{\bigg(\dfrac{44}{21},-\dfrac{29}{21}\bigg)\bigg\}}}}}\blue{\checkmark}$