Đáp án:
b. x=2
Giải thích các bước giải:
\(\begin{array}{l}
a.4 - 11x + 7{x^2} = x - 1\\
\to 7{x^2} - 12x + 5 = 0\\
\to 7{x^2} - 7x - 5x + 5 = 0\\
\to 7x\left( {x - 1} \right) - 5\left( {x - 1} \right) = 0\\
\to \left( {x - 1} \right)\left( {7x - 5} \right) = 0\\
\to \left[ \begin{array}{l}
x = 1\\
x = \dfrac{5}{7}
\end{array} \right.\\
Do:x \ne 1\\
\to x = \dfrac{5}{7}\\
b.{x^3} - x = 2{x^2} - 2\\
\to {x^3} - 2{x^2} - x + 2 = 0\\
\to {x^3} - {x^2} - {x^2} + x - 2x + 2 = 0\\
\to {x^2}\left( {x - 1} \right) - x\left( {x - 1} \right) - 2\left( {x - 1} \right) = 0\\
\to \left( {x - 1} \right)\left( {{x^2} - x - 2} \right) = 0\\
\to \left[ \begin{array}{l}
x = 1\\
\left( {x - 2} \right)\left( {x + 1} \right) = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 1\\
x = - 1\\
x = 2
\end{array} \right.\\
Do:x \ne \pm 1\\
\to x = 2
\end{array}\)
