Bài 1:
a) Ta có: \(\frac{5}{6}-\frac{2}{3}+\frac{1}{4}\)
\(=\frac{10}{12}-\frac{8}{12}+\frac{3}{12}\)
\(=\frac{2+3}{12}=\frac{5}{12}\)
b) Ta có: \(1\frac{11}{12}-\frac{5}{12}\cdot\left(\frac{4}{5}-\frac{1}{10}\right):\frac{-5}{12}\)
\(=\frac{23}{12}-\frac{5}{12}\cdot\left(\frac{8}{10}-\frac{1}{10}\right)\cdot\frac{-12}{5}\)
\(=\frac{23}{12}-\frac{5}{12}\cdot\frac{7}{10}\cdot\frac{-12}{5}\)
\(=\frac{23}{12}-\frac{-7}{10}\)
\(=\frac{115}{60}+\frac{42}{60}=\frac{157}{60}\)
Bài 2:
a) Ta có: \(\frac{1}{2}\cdot x-\frac{2}{5}=\frac{1}{5}\)
\(\Leftrightarrow\frac{1}{2}\cdot x=\frac{1}{5}+\frac{2}{5}=\frac{3}{5}\)
\(\Leftrightarrow x=\frac{3}{5}:\frac{1}{2}=\frac{3}{5}\cdot2=\frac{6}{5}\)
Vậy: \(x=\frac{6}{5}\)
b) Ta có: \(\left(1-2x\right)\cdot\frac{4}{3}=\left(-2\right)^3\)
\(\Leftrightarrow\left(1-2x\right)\cdot\frac{4}{3}=-8\)
\(\Leftrightarrow1-2x=-8:\frac{4}{3}=-8\cdot\frac{3}{4}=-6\)
\(\Leftrightarrow-2x=-6-1=-7\)
hay \(x=\frac{7}{2}\)
Vậy: \(x=\frac{7}{2}\)
Bài 1:
a) Ta có: 56−23+1456−23+14
=1012−812+312=1012−812+312
=2+312=512=2+312=512
b) Ta có: 11112−512⋅(45−110):−51211112−512⋅(45−110):−512
=2312−512⋅(810−110)⋅−125=2312−512⋅(810−110)⋅−125
=2312−512⋅710⋅−125=2312−512⋅710⋅−125
=2312−−710=2312−−710
=11560+4260=15760=11560+4260=15760
Bài 2:
a) Ta có: 12⋅x−25=1512⋅x−25=15
⇔12⋅x=15+25=35⇔12⋅x=15+25=35
⇔x=35:12=35⋅2=65⇔x=35:12=35⋅2=65
Vậy: x=65x=65
b) Ta có: (1−2x)⋅43=(−2)3(1−2x)⋅43=(−2)3
⇔(1−2x)⋅43=−8⇔(1−2x)⋅43=−8
⇔1−2x=−8:43=−8⋅34=−6⇔1−2x=−8:43=−8⋅34=−6
⇔−2x=−6−1=−7⇔−2x=−6−1=−7
hay x=72x=72
Vậy: x=72
