a: =>x+2/5=11/12-2/3=11/12-8/12=3/12=1/4
=>x=1/4-2/5=5/20-8/20=-3/20
b: =>x=0 hoặc x-1/7=0
=>x=0 hoặc x=1/7
c: =>1/4:x=2/5-3/4=-7/20
=>x=-1/4:7/20=-1/4x20/7=-20/28=-5/7
\(a,\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\)
\(\dfrac{2}{5}+x=\dfrac{11}{12}-\dfrac{2}{3}\)
\(\dfrac{2}{5}+x=\dfrac{1}{4}\)
\(x=\dfrac{1}{4}-\dfrac{2}{5}\)
\(x=\dfrac{-3}{20}\)
Vậy \(x=-\dfrac{3}{20}\)
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\(b,2x\left(x-\dfrac{1}{7}\right)=0\)
\(2x=0\) hoặc \(x-\dfrac{1}{7}=0\)
\(x=0\) hoặc \(x=\dfrac{1}{7}\)
Vậy \(x=0\) hoặc \(x=\dfrac{1}{7}\)
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\(c,\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)
\(\dfrac{1}{4}:x=\dfrac{2}{5}-\dfrac{3}{4}\)
\(\dfrac{1}{4}:x=\dfrac{-7}{20}\)
\(x=\dfrac{1}{4}:-\dfrac{7}{20}\)
\(x=-\dfrac{5}{7}\)
Vậy \(x=-\dfrac{5}{7}\)
