Đáp án:
\(\begin{array}{l}
x = - 4\\
\to \left\{ \begin{array}{l}
y = - 6\\
z = - 10
\end{array} \right.
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a.5x - 3 - 2x - 6 = x + 1 - 2x + 20\\
\to 4x = 30\\
\to x = \frac{{30}}{4} = \frac{{15}}{2}\\
b.\left\{ \begin{array}{l}
\frac{x}{2} = \frac{y}{3}\\
\frac{x}{2} = \frac{z}{5}\\
x + y - 2z = 10
\end{array} \right.\\
\to \left\{ \begin{array}{l}
\frac{3}{2}x = y\\
z = \frac{5}{2}x\\
x + \frac{3}{2}x - 2.\frac{5}{2}x = 10\left( * \right)
\end{array} \right.\\
\left( * \right) \to x + \frac{3}{2}x - 5x = 10\\
\to \left( {1 + \frac{3}{2} - 5} \right)x = 10\\
\to - \frac{5}{2}x = 10\\
\to x = - 4\\
\to \left\{ \begin{array}{l}
y = - 6\\
z = - 10
\end{array} \right.
\end{array}\)
