Đáp án: $\left( {x;y} \right) = \left( {\dfrac{{ - 8}}{3};\dfrac{{11}}{3}} \right)$
Giải thích các bước giải:
$\begin{array}{l}
\left\{ \begin{array}{l}
x + y = 1\left( 1 \right)\\
2y - x = 10\left( 2 \right)
\end{array} \right.\\
\left( 1 \right) + \left( 2 \right) \Leftrightarrow x + y + 2y - x = 1 + 10\\
\Leftrightarrow 3y = 11\\
\Leftrightarrow y = \dfrac{{11}}{3}\\
\left( 1 \right):x + y = 1 \Leftrightarrow x = 1 - y = 1 - \dfrac{{11}}{3} = \dfrac{{ - 8}}{3}\\
Vậy\,\left( {x;y} \right) = \left( {\dfrac{{ - 8}}{3};\dfrac{{11}}{3}} \right)
\end{array}$
