Toán Lớp 8: a. x-5x+2/6=7-3x/4
b. |x-5|+|25-x^2|=0
c. |x+1|-|3-2x|=0
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Toán Lớp 8: a. x-5x+2/6=7-3x/4
b. |x-5|+|25-x^2|=0
c. |x+1|-|3-2x|=0
Giúp em với ạ:<<
Comments ( 1 )
a)x – \dfrac{{5x + 2}}{6} = \dfrac{{7 – 3x}}{4}\\
\Leftrightarrow \dfrac{{12x – 10x – 4}}{{12}} = \dfrac{{21 – 9x}}{{12}}\\
\Leftrightarrow 2x – 4 = 21 – 9x\\
\Leftrightarrow 11x = 25\\
\Leftrightarrow x = \dfrac{{25}}{{11}}\\
Vậy\,x = \dfrac{{25}}{{11}}\\
b)\left| {x – 5} \right| + \left| {25 – {x^2}} \right| = 0\\
\Leftrightarrow \left| {x – 5} \right| + \left| {x – 5} \right|.\left| {x + 5} \right| = 0\\
\Leftrightarrow \left| {x – 5} \right|.\left( {\left| {x + 5} \right| + 1} \right) = 0\\
\Leftrightarrow \left| {x – 5} \right| = 0\\
\Leftrightarrow x = 5\\
Vậy\,x = 5\\
c)\left| {x + 1} \right| – \left| {3 – 2x} \right| = 0\\
\Leftrightarrow \left| {x + 1} \right| = \left| {3 – 2x} \right|\\
\Leftrightarrow \left[ \begin{array}{l}
x + 1 = 3 – 2x\\
x + 1 = 2x – 3
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = \dfrac{2}{3}\\
x = 4
\end{array} \right.\\
Vậy\,x = \dfrac{2}{3};x = 4
\end{array}$