Đáp án:
\(\left\{ \begin{array}{l}
b = \dfrac{3}{4}\\
a = - \dfrac{9}{4}
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
DK:b \ne 0\\
\left\{ \begin{array}{l}
a - b = 2\left( {a + b} \right)\\
a - b = \dfrac{a}{b}
\end{array} \right.\\
\to \left\{ \begin{array}{l}
a - b = 2a + 2b\\
a - b = \dfrac{a}{b}
\end{array} \right.\\
\to \left\{ \begin{array}{l}
a = - 3b\\
- 3b - b = \dfrac{{ - 3b}}{b}
\end{array} \right.\\
\to \left\{ \begin{array}{l}
a = - 3b\\
- 4b = - 3
\end{array} \right.\\
\to \left\{ \begin{array}{l}
b = \dfrac{3}{4}\\
a = - 3.\dfrac{3}{4} = - \dfrac{9}{4}
\end{array} \right.
\end{array}\)
