Toán Lớp 7: a)(3/5x-2/3x-x).1/7=-5/12
b) (5x-1).(2x+1/3)=0
c) 2/3:x+6=4
d) 5.(x+2)^3+7=2
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Toán Lớp 7: a)(3/5x-2/3x-x).1/7=-5/12
b) (5x-1).(2x+1/3)=0
c) 2/3:x+6=4
d) 5.(x+2)^3+7=2
giúp mình với, mình đang cần gấp
Comments ( 1 )
a)\left( {\dfrac{3}{5}x – \dfrac{2}{3}x – x} \right).\dfrac{1}{7} = \dfrac{{ – 5}}{{12}}\\
\Leftrightarrow x.\left( {\dfrac{3}{5} – \dfrac{2}{3} – 1} \right).\dfrac{1}{7} = – \dfrac{5}{{12}}\\
\Leftrightarrow x.\dfrac{{ – 16}}{{15}}.\dfrac{1}{7} = – \dfrac{5}{{12}}\\
\Leftrightarrow x = – \dfrac{5}{{12}}.\dfrac{{ – 15.7}}{{16}}\\
\Leftrightarrow x = \dfrac{{175}}{{64}}\\
Vậy\,x = \dfrac{{175}}{{64}}\\
b)\left( {5x – 1} \right)\left( {2x + \dfrac{1}{3}} \right) = 0\\
\Leftrightarrow \left[ \begin{array}{l}
5x – 1 = 0\\
2x + \dfrac{1}{3} = 0
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = \dfrac{1}{5}\\
x = – \dfrac{1}{6}
\end{array} \right.\\
Vậy\,x = \dfrac{1}{5};x = – \dfrac{1}{6}\\
c)\dfrac{2}{3}:x + 6 = 4\\
\Leftrightarrow \dfrac{2}{3}:x = – 2\\
\Leftrightarrow x = \dfrac{2}{3}:\left( { – 2} \right)\\
\Leftrightarrow x = – \dfrac{1}{3}\\
Vậy\,x = – \dfrac{1}{3}\\
d)5.{\left( {x + 2} \right)^3} + 7 = 2\\
\Leftrightarrow 5.{\left( {x + 2} \right)^3} = – 5\\
\Leftrightarrow {\left( {x + 2} \right)^3} = – 1\\
\Leftrightarrow x + 2 = – 1\\
\Leftrightarrow x = – 3\\
Vậy\,x = – 3
\end{array}$