Đáp án:
B3:
c) \(x = - \dfrac{8}{3}\)
Giải thích các bước giải:
\(\begin{array}{l}
B1:\\
a)\left[ \begin{array}{l}
x - 2 = 0\\
x + 3 = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 2\\
x = - 3
\end{array} \right.\\
d)\left( {3x - 1} \right)\left( {{x^2} + 2} \right) - \left( {3x - 1} \right)\left( {7x - 10} \right) = 0\\
\to \left( {3x - 1} \right)\left( {{x^2} + 2 - 7x + 10} \right) = 0\\
\to \left[ \begin{array}{l}
3x - 1 = 0\\
{x^2} - 7x + 12 = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = \dfrac{1}{3}\\
\left( {x - 3} \right)\left( {x - 4} \right) = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 3\\
x = 4\\
x = \dfrac{1}{3}
\end{array} \right.\\
b)\left[ \begin{array}{l}
2x + 1 = 0\\
2x - 1 = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = - \dfrac{1}{2}\\
x = \dfrac{1}{2}
\end{array} \right.\\
e)\dfrac{3}{7}x - 1 = \dfrac{1}{7}x\left( {3x - 7} \right)\\
\to \left( {\dfrac{3}{7}x - 1} \right) - x\left( {\dfrac{3}{7}x - 1} \right) = 0\\
\to \left( {\dfrac{3}{7}x - 1} \right)\left( {1 - x} \right) = 0\\
\to \left[ \begin{array}{l}
x = 1\\
x = \dfrac{7}{3}
\end{array} \right.\\
B2:\\
a)DK:x - 2 \ne 0\\
\to x \ne 2\\
b)DK:\left\{ \begin{array}{l}
x - 1 \ne 0\\
x + 2 \ne 0
\end{array} \right.\\
\to x \ne \left\{ { - 2;1} \right\}\\
B3:\\
b)DK:x \ne - 5\\
Pt \to 2x - 3 = 3\left( {x + 5} \right)\\
\to 2x - 3 = 3x + 15\\
\to x = - 18\\
c)DK:x \ne \left\{ {0;2} \right\}\\
Pt \to 2\left( {x - 2} \right)\left( {x + 2} \right) = x\left( {2x + 3} \right)\\
\to 2{x^2} - 8 = 2{x^2} + 3x\\
\to x = - \dfrac{8}{3}
\end{array}\)
