Toán Lớp 7: Tìm x
| x – 3 | + | 2x + 2 | = 0
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Toán Lớp 7: Tìm x
| x – 3 | + | 2x + 2 | = 0
Comments ( 1 )
Do:\left\{ \begin{array}{l}
\left| {x – 3} \right| \ge 0\\
\left| {2x + 2} \right| \ge 0
\end{array} \right.\\
\Leftrightarrow \left| {x – 3} \right| + \left| {2x + 2} \right| \ge 0\\
Khi:\left| {x – 3} \right| + \left| {2x + 2} \right| = 0\\
\Leftrightarrow \left\{ \begin{array}{l}
\left| {x – 3} \right| = 0\\
\left| {2x + 2} \right| = 0
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
x = 3\\
2x + 2 = 0
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
x = 3\\
x = – 1
\end{array} \right.\left( {ktm} \right)
\end{array}$