Đáp án:
d. \(\left\{ \begin{array}{l}
y = 7\\
x = 10
\end{array} \right.\)
e. \(\left\{ \begin{array}{l}
x = - 5\\
y = 5
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
d.\left\{ \begin{array}{l}
x - y = 3\\
3x - 4y = 2
\end{array} \right. \to \left\{ \begin{array}{l}
x = 3 + y\\
9 + 3y - 4y = 2
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = 7\\
x = 10
\end{array} \right.\\
e.\left\{ \begin{array}{l}
x + 2y = 5\\
3x + 4y = 5
\end{array} \right. \to \left\{ \begin{array}{l}
2x + 4y = 10\\
3x + 4y = 5
\end{array} \right.\\
\to \left\{ \begin{array}{l}
- x = 5\\
3x + 4y = 5
\end{array} \right. \to \left\{ \begin{array}{l}
x = - 5\\
y = 5
\end{array} \right.\\
f.\left\{ \begin{array}{l}
5x + 7y = 6\\
4x + 3y = 2
\end{array} \right. \to \left\{ \begin{array}{l}
20x + 28y = 24\\
20x + 15y = 10
\end{array} \right.\\
\to \left\{ \begin{array}{l}
13y = 14\\
4x + 3y = 2
\end{array} \right. \to \left\{ \begin{array}{l}
y = \frac{{14}}{{13}}\\
x = - \frac{4}{{13}}
\end{array} \right.\\
g.\left\{ \begin{array}{l}
x + 4y = 2\\
4x - 3y = 1
\end{array} \right. \to \left\{ \begin{array}{l}
x = 2 - 4y\\
8 - 16y - 3y = 1
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 2 - 4y\\
y = \frac{7}{{19}}
\end{array} \right. \to \left\{ \begin{array}{l}
x = \frac{{10}}{{19}}\\
y = \frac{7}{{19}}
\end{array} \right.
\end{array}\)
