Đáp án:
f. \(\left\{ \begin{array}{l}
y = - 120\\
x = - 84
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\left\{ \begin{array}{l}
x = - 2y\\
- 2y + y = 12
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = - 12\\
x = 24
\end{array} \right.\\
b.\left\{ \begin{array}{l}
y = 4x\\
x - 4x = - 15
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 5\\
y = 20
\end{array} \right.\\
c.\left\{ \begin{array}{l}
x = \dfrac{3}{5}y\\
\dfrac{3}{5}y - y = 32
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = - 80\\
x = - 48
\end{array} \right.\\
d.\left\{ \begin{array}{l}
x = \dfrac{7}{3}y\\
\dfrac{7}{3}y + y = 40
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = 12\\
x = 28
\end{array} \right.\\
e.\left\{ \begin{array}{l}
x = \dfrac{5}{9}y\\
\dfrac{5}{9}y + y = 56
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = 36\\
x = 20
\end{array} \right.\\
f.\left\{ \begin{array}{l}
x = \dfrac{7}{{10}}y\\
\dfrac{7}{{10}}y - y = 36
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = - 120\\
x = - 84
\end{array} \right.
\end{array}\)
