Toán Lớp 7: Tìm x biết :
a) 2-/x+1/=2x .
b) 3/x+2/-2/x+3/=0
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Toán Lớp 7: Tìm x biết :
a) 2-/x+1/=2x .
b) 3/x+2/-2/x+3/=0
Comments ( 1 )
a)x = \dfrac{1}{3}\\
b)\left[ \begin{array}{l}
x = 0\\
x = – \dfrac{{12}}{5}
\end{array} \right.
\end{array}\)
a)2 – \left| {x + 1} \right| = 2x\\
\to \left| {x + 1} \right| = 2 – 2x\\
\to \left[ \begin{array}{l}
x + 1 = 2 – 2x\left( {DK:x \ge – 1} \right)\\
x + 1 = – 2 + 2x\left( {DK:x < – 1} \right)
\end{array} \right.\\
\to \left[ \begin{array}{l}
3x = 1\\
x = 3\left( l \right)
\end{array} \right.\\
\to x = \dfrac{1}{3}\\
b)3\left| {x + 2} \right| – 2\left| {x + 3} \right| = 0\\
\to 3\left| {x + 2} \right| = 2\left| {x + 3} \right|\\
\to \left[ \begin{array}{l}
3\left( {x + 2} \right) = 2\left( {x + 3} \right)\left( {DK:x \ge – 2} \right)\\
3\left( { – x – 2} \right) = 2\left( {x + 3} \right)\left( {DK: – 2 > x \ge – 3} \right)\\
3\left( { – x – 2} \right) = 2\left( { – x – 3} \right)\left( {DK: – 3 > x} \right)
\end{array} \right.\\
\to \left[ \begin{array}{l}
3x + 6 = 2x + 6\\
– 3x – 6 = 2x + 6\\
– 3x – 6 = – 2x – 6
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 0\\
5x = – 12\\
x = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 0\\
x = – \dfrac{{12}}{5}
\end{array} \right.
\end{array}\)