Toán Lớp 8: giải phương trình:
$x^{2}+x=2x+2$
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Toán Lớp 8: giải phương trình:
$x^{2}+x=2x+2$
Comments ( 2 )
{x^2} + x = 2x + 2\\
\Leftrightarrow {x^2} + x – 2x – 2 = 0\\
\Leftrightarrow x\left( {x + 1} \right) – 2\left( {x + 1} \right) = 0\\
\Leftrightarrow \left( {x – 2} \right)\left( {x + 1} \right) = 0\\
\Leftrightarrow \left[ \begin{array}{l}
x – 2 = 0\\
x + 1 = 0
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = 2\\
x = – 1
\end{array} \right.\\
\Rightarrow S \in \left\{ {2; – 1} \right\}
\end{array}\]