Đáp án:
a. \(\left[ \begin{array}{l}
x = 7\\
x = - 4
\end{array} \right.\)
b. \(\left[ \begin{array}{l}
x = 2\\
x = \frac{5}{3}
\end{array} \right.\)
c. \(\left[ \begin{array}{l}
x = - 2\\
x = \frac{5}{3}
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\left[ \begin{array}{l}
x - 7 = 0\\
2x + 8 = 0
\end{array} \right. \to \left[ \begin{array}{l}
x = 7\\
x = - 4
\end{array} \right.\\
c.3x\left( {x - 2} \right) - 5\left( {x - 2} \right) = 0\\
\to \left( {x - 2} \right)\left( {3x - 5} \right) = 0\\
\to \left[ \begin{array}{l}
x - 2 = 0\\
3x - 5 = 0
\end{array} \right. \to \left[ \begin{array}{l}
x = 2\\
x = \frac{5}{3}
\end{array} \right.\\
d.\left( {x + 2} \right)\left( {3 - 4x} \right) + {\left( {x + 2} \right)^2} = 0\\
\to \left( {x + 2} \right)\left( {3 - 4x + x + 2} \right) = 0\\
\to \left[ \begin{array}{l}
x + 2 = 0\\
- 3x + 5 = 0
\end{array} \right. \to \left[ \begin{array}{l}
x = - 2\\
x = \frac{5}{3}
\end{array} \right.
\end{array}\)