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â, -4/9(7/15+8/15)=-4/9
b,-5/4(16/25+9/25)=-5/4
,.....
dài quá mik làm ko hết
hok tốt
\(A=\left(\frac{3}{8}+\frac{-3}{4}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)
\(A=\left(\frac{3}{8}+\frac{-6}{8}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)
\(A=\left(\frac{-3}{8}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)
\(A=\left(\frac{-36}{24}+\frac{56}{24}\right):\frac{5}{6}+\frac{1}{2}\)
\(A=\frac{5}{6}:\frac{5}{6}+\frac{1}{2}\)
\(A=\frac{5}{6}\times\frac{6}{5}+\frac{1}{2}\)
\(A=1+\frac{1}{2}\)
\(A=\frac{1}{1}+\frac{1}{2}=\frac{2}{2}+\frac{1}{2}\)
\(A=\frac{3}{2}\)
a)\(\frac{2}{7}+\frac{3}{8}=\frac{16}{56}+\frac{21}{56}=\frac{37}{56}\)
b)\(\frac{7}{56}:\frac{20}{25}=\frac{6}{56}x\frac{25}{20}=\frac{150}{1120}=\frac{15}{112}\)
c)\(\frac{20}{35}x\frac{5}{4}=\frac{100}{140}=\frac{5}{7}\)
d)\(\frac{8}{7}-\frac{5}{6}=\frac{48}{56}-\frac{35}{56}=\frac{13}{56}\)
b) \(\frac{-5\cdot7^5+7^4}{7^6\cdot10-2\cdot7^5}\)
\(=\frac{-35\cdot7^4+7^4}{7^5\cdot70-2\cdot7^5}\)
\(=\frac{7^4\left(-35+1\right)}{7^5\left(70-2\right)}\)
\(=\frac{7^4\cdot\left(-34\right)}{7^5\cdot68}\)
\(=\frac{-1}{14}\)
Chắc sai =))