Đáp án:
d. \(\left\{ \begin{array}{l}
y = - \frac{7}{2}\\
x = \frac{5}{8}
\end{array} \right.\)
Giải thích các bước giải:
Bài 1:
\(\begin{array}{l}
a.\left\{ \begin{array}{l}
2x + x = 5 + 1\\
x + y = 1
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 2\\
y = - 1
\end{array} \right.\\
c.\left\{ \begin{array}{l}
3x + 2x = 3 + 7\\
2x - y = 7
\end{array} \right.\\
\to \left\{ \begin{array}{l}
5x = 10\\
y = 2x - 7
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 2\\
y = - 3
\end{array} \right.\\
b.\left\{ \begin{array}{l}
4x - 2y = - 2\\
5x - 2y = 4
\end{array} \right.\\
\to \left\{ \begin{array}{l}
5x - 4x = 4 - \left( { - 2} \right)\\
2x - y = - 1
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 6\\
y = 2.6 + 1
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 6\\
y = 13
\end{array} \right.\\
d.DK:x \ne 1;y \ne - 2\\
\left\{ \begin{array}{l}
\frac{{2y - \left( { - y} \right)}}{{y + 2}} = 3 - \left( { - 4} \right)\\
\frac{x}{{x - 1}} - \frac{y}{{y + 2}} = - 4
\end{array} \right.\\
\to \left\{ \begin{array}{l}
\frac{{3y}}{{y + 2}} = 7\\
\frac{x}{{x - 1}} = \frac{y}{{y + 2}} - 4
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = - \frac{7}{2}\\
\frac{x}{{x - 1}} = - \frac{5}{3}
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = - \frac{7}{2}\\
x = \frac{5}{8}
\end{array} \right.\left( {TM} \right)
\end{array}\)
Bài 2:
\(\begin{array}{l}
a.3x - y = 2\\
\to y = 3x - 2\\
b.x + y = 1\\
\to y = - x + 1
\end{array}\)
