Đáp án:
h) \(\left\{ \begin{array}{l}
y = 36\\
x = 27\\
z = 60
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
b)\left\{ \begin{array}{l}
5x = 8y\\
- x + 2y = - 12
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 2y + 12\\
5\left( {2y + 12} \right) = 8y
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 2y + 12\\
10y + 60 = 8y
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 2y + 12\\
2y = - 60
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = - 30\\
x = - 48
\end{array} \right.\\
f)\left\{ \begin{array}{l}
7x - 2y = 5x - 3y\\
2x + 3y = - 20
\end{array} \right.\\
\to \left\{ \begin{array}{l}
2x = - y\\
2x + 3y = - 20
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = - 2x\\
2x + 3\left( { - 2x} \right) = - 20
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = - 2x\\
- 4x = - 20
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 5\\
y = - 10
\end{array} \right.\\
h)\left\{ \begin{array}{l}
x = \dfrac{3}{4}y\\
z = \dfrac{5}{3}y\\
2.\dfrac{3}{4}y - 3y + \dfrac{5}{3}y = 6
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = \dfrac{3}{4}y\\
z = \dfrac{5}{3}y\\
\left( {\dfrac{3}{2} - 3 + \dfrac{5}{3}} \right)y = 6
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = \dfrac{3}{4}y\\
z = \dfrac{5}{3}y\\
\dfrac{1}{6}y = 6
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = 36\\
x = 27\\
z = 60
\end{array} \right.
\end{array}\)
