a) \(\dfrac{2}{3}+\dfrac{4}{9}=\dfrac{6}{9}+\dfrac{4}{9}+\dfrac{6+3}{9}=\dfrac{10}{9}\)

b)\(\dfrac{1}{10}+\dfrac{2}{5}=\dfrac{1}{10}+\dfrac{4}{10}=\dfrac{1+4}{10}=\dfrac{5}{10}=\dfrac{1}{2}\)

c) \(\dfrac{7}{22}-\dfrac{3}{11}=\dfrac{7}{22}-\dfrac{6}{22}=\dfrac{7-6}{22}=\dfrac{1}{22}\)

d) \(\dfrac{5}{6}-\dfrac{5}{12}=\dfrac{10}{12}-\dfrac{5}{12}=\dfrac{10-5}{12}=\dfrac{5}{12}\)

a) \(\dfrac{9}{11}-\dfrac{3}{11}=\dfrac{9-3}{11}=\dfrac{6}{11}\)

b) \(\dfrac{10}{4}-\dfrac{5}{4}=\dfrac{10-5}{4}=\dfrac{5}{4}\)

c) \(\dfrac{22}{15}-\dfrac{8}{15}=\dfrac{22-8}{15}=\dfrac{14}{15}\)

\(a,A=\dfrac{\dfrac{5}{4}+\dfrac{5}{5}+\dfrac{5}{7}-\dfrac{5}{11}}{\dfrac{10}{4}+\dfrac{10}{5}+\dfrac{10}{7}-\dfrac{10}{11}}\\ =\dfrac{5.\left(\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{1}{7}-\dfrac{1}{11}\right)}{10.\left(\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{1}{7}-\dfrac{1}{11}\right)}\\ =\dfrac{5}{10}\\ =\dfrac{1}{2}\)

Vậy \(A=\dfrac{1}{2}\)

\(b,B=\dfrac{2+\dfrac{6}{5}-\dfrac{6}{7}-\dfrac{6}{11}}{\dfrac{2}{3}+\dfrac{2}{5}-\dfrac{2}{7}-\dfrac{2}{11}}\\ =\dfrac{3.\left(\dfrac{2}{3}+\dfrac{2}{5}-\dfrac{2}{7}-\dfrac{2}{11}\right)}{\dfrac{2}{3}+\dfrac{2}{5}-\dfrac{2}{7}-\dfrac{2}{11}}\\ =3\)

Vậy \(B=3\)

a,A,C,D

b,C

a) Câu A;D

b) Câu C

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Hết à bạn

a: \(=\dfrac{11}{21}+\dfrac{10}{21}+\dfrac{-2}{7}+\dfrac{-5}{7}-\dfrac{6}{5}=\dfrac{-6}{5}\)

b: \(=\left[0.25\cdot\left(-4\right)\right]^5\cdot\left(-\dfrac{50}{9}\right)\)

=50/9

c: \(=\dfrac{3}{22}\left(19+\dfrac{1}{7}+2+\dfrac{6}{7}\right)-6\)

\(=\dfrac{3}{22}\cdot22-6=3-6=-3\)

3.a)\(\dfrac{-1}{2}+\dfrac{5}{6}+\dfrac{1}{3}=\dfrac{-3}{6}+\dfrac{5}{6}+\dfrac{2}{6}=\dfrac{-3+5+2}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)

   b)\(\dfrac{-3}{8}+\dfrac{7}{4}-\dfrac{1}{12}=\dfrac{-9}{24}+\dfrac{42}{24}-\dfrac{2}{24}=\dfrac{-9+42-2}{24}=\dfrac{31}{24}\)

   c)\(\dfrac{3}{5}:\left(\dfrac{1}{4}.\dfrac{7}{5}\right)=\dfrac{3}{5}:\dfrac{7}{20}=\dfrac{3}{5}.\dfrac{20}{7}=\dfrac{12}{7}\)

   d)\(\dfrac{10}{11}+\dfrac{4}{11}:4-\dfrac{1}{8}=\dfrac{10}{11}+\dfrac{4}{11}.\dfrac{1}{4}-\dfrac{1}{8}=\dfrac{10}{11}+\dfrac{1}{11}-\dfrac{1}{8}=1-\dfrac{1}{8}=\dfrac{8}{8}-\dfrac{1}{8}=\dfrac{7}{8}\)

a: \(\dfrac{-1}{2}+\dfrac{5}{6}+\dfrac{1}{3}\)

\(=\dfrac{-3}{6}+\dfrac{5}{6}+\dfrac{2}{6}\)

\(=\dfrac{4}{6}=\dfrac{2}{3}\)

b: \(\dfrac{-3}{8}+\dfrac{7}{4}-\dfrac{1}{12}\)

\(=\dfrac{-9}{24}+\dfrac{42}{24}-\dfrac{2}{24}\)

\(=\dfrac{31}{24}\)

c: \(\dfrac{3}{5}:\left(\dfrac{1}{4}\cdot\dfrac{7}{5}\right)=\dfrac{3}{4}:\dfrac{7}{20}=\dfrac{3}{4}\cdot\dfrac{20}{7}=\dfrac{15}{7}\)

d: \(\dfrac{10}{11}+\dfrac{4}{11}:4-\dfrac{1}{8}\)

\(=\dfrac{10}{11}+\dfrac{1}{11}-\dfrac{1}{8}=\dfrac{7}{8}\)

a: Sửa đề: \(\left(6:\frac35-1\frac16\times\frac67\right):\left(4\frac15\times\frac{10}{11}+5\frac{2}{11}\right)\)

Ta có: \(\left(6:\frac35-1\frac16\times\frac67\right):\left(4\frac15\times\frac{10}{11}+5\frac{2}{11}\right)\)

\(=\left(6\times\frac53-\frac76\times\frac67\right):\left(\frac{21}{5}\times\frac{10}{11}+5+\frac{2}{11}\right)\)

\(=\left(10-1\right):\left(21\times\frac{2}{11}+5+\frac{2}{11}\right)\)

\(=9:\left(\frac{2}{11}\times22+5\right)=9:\left(4+5\right)=\frac99=1\)

b: Sửa đề: \(\left(1-\frac12\right)\times\left(1-\frac13\right)\times\ldots\times\left(1-\frac{1}{2006}\right)\times\left(1-\frac{1}{2007}\right)\)

Ta có: \(\left(1-\frac12\right)\times\left(1-\frac13\right)\times\ldots\times\left(1-\frac{1}{2006}\right)\times\left(1-\frac{1}{2007}\right)\)

\(=\frac12\times\frac23\times\ldots\times\frac{2005}{2006}\times\frac{2006}{2007}\)

\(=\frac{1}{2007}\)