Bài 2 :
\(a,PT\Leftrightarrow\dfrac{11}{13}-\dfrac{5}{42}+x=-\dfrac{15}{28}+\dfrac{11}{13}\)
\(\Leftrightarrow x=-\dfrac{15}{28}+\dfrac{11}{13}-\dfrac{11}{13}+\dfrac{5}{42}=-\dfrac{5}{12}\)
Vậy ....
\(b,PT\Leftrightarrow x=\dfrac{2}{5}+\dfrac{1}{3}-\dfrac{1}{3}=\dfrac{2}{5}\)
Vậy ...
\(c,PT\Leftrightarrow\dfrac{2}{3}x=\dfrac{3}{10}-\dfrac{5}{7}=-\dfrac{29}{70}\)
\(\Leftrightarrow x=-\dfrac{87}{140}\)
Vậy ...
\(d,PT\Leftrightarrow x=\dfrac{3}{7}-\dfrac{1}{4}+\left(-\dfrac{3}{5}\right)=-\dfrac{59}{140}\)
Vậy ...
\(e,PT\Leftrightarrow\dfrac{-21}{13}x=-\dfrac{2}{3}-\dfrac{1}{3}=-1\)
\(\Leftrightarrow x=\dfrac{13}{21}\)
Vậy ...
Bài 3 :
a, \(PT\Leftrightarrow\dfrac{2}{5}+x=\dfrac{11}{12}-\dfrac{2}{3}=\dfrac{1}{4}\)
\(\Leftrightarrow x=\dfrac{1}{4}-\dfrac{2}{5}=-\dfrac{3}{20}\)
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b,\(PT\Leftrightarrow\left[{}\begin{matrix}2x=0\\x-\dfrac{1}{7}=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{7}\end{matrix}\right.\)
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c, \(PT\Leftrightarrow\dfrac{1}{4x}=\dfrac{2}{5}-\dfrac{3}{4}=-\dfrac{7}{20}\)
\(\Leftrightarrow4x=-\dfrac{20}{7}\)
\(\Leftrightarrow x=-\dfrac{5}{7}\)
Vậy .....