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24 tháng 4 2021

\(A=\frac{12}{19}\cdot\frac{7}{15}\cdot\left(-\frac{13}{17}\right)\cdot\frac{19}{12}\cdot\frac{17}{13}\)

\(A=\left(\frac{12}{19}\cdot\frac{19}{12}\right)\cdot\left(-\frac{13}{17}\cdot\frac{17}{13}\right)\cdot\frac{7}{15}\)

\(A=1\cdot\left(-1\right)\cdot\frac{7}{15}\)

\(A=-\frac{7}{15}\)

28 tháng 4 2021

\(\left(\frac{12}{19}.\frac{19}{12}\right).\left(\frac{-13}{17}.\frac{17}{13}\right).\frac{7}{15}\)

\(=1.\left(-1\right).\frac{7}{15}\)

\(=-\frac{7}{15}\)

a: \(=\dfrac{17}{19}\cdot\dfrac{19}{17}\cdot\dfrac{4}{5}=\dfrac{4}{5}\)

b: \(=\dfrac{14}{7}\cdot\dfrac{7}{6}=2\cdot\dfrac{7}{6}=\dfrac{14}{6}=\dfrac{7}{3}\)

c: =13/14(4/5+1/5)=13/14

9 tháng 3 2022

\(\dfrac{17}{19}\times\dfrac{12}{15}\times\dfrac{19}{17}=\dfrac{12}{15}\)

\(\left(\dfrac{5}{7}+\dfrac{9}{7}\right)\times\dfrac{21}{18}=2\times\dfrac{7}{6}=\dfrac{7}{3}\)

\(\dfrac{4}{5}\times\dfrac{13}{14}+\dfrac{13}{14}\times\dfrac{1}{5}=\dfrac{13}{14}\)

9 tháng 3 2022

\(\dfrac{17}{19}\times\dfrac{12}{15}\times\dfrac{19}{17}.\\ =\dfrac{17}{19}\times\dfrac{19}{17}\times\dfrac{12}{15}.\\ =1\times\dfrac{12}{15}=\dfrac{12}{15}.\\ \left(\dfrac{5}{7}+\dfrac{9}{7}\right)\times\dfrac{21}{18}.\\ =2\times\dfrac{7}{6}=\dfrac{7}{3}.\\ \dfrac{4}{5}\times\dfrac{13}{14}+\dfrac{13}{14}\times\dfrac{1}{5}.\\ =\left(\dfrac{4}{5}+\dfrac{1}{5}\right)\times\dfrac{13}{14}.\\ =1\times\dfrac{13}{14}.\\ =\dfrac{13}{14}.\)

25 tháng 3 2021

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bằng2527/3420

mik rut gọn rồi 

đúng thì

đúng thì k

a) \(-\frac{5}{7}.\frac{2}{11}+\left(-\frac{5}{7}\right).\frac{9}{14}+1.\left(-\frac{5}{7}\right)\)

\(=-\frac{5}{7}.\left(\frac{2}{11}+\frac{9}{14}+1\right)\)

\(=-\frac{5}{7}.\frac{281}{154}\)

\(=-\frac{1405}{1078}\)

Vậy : \(-\frac{5}{7}.\frac{2}{11}+\left(-\frac{5}{7}\right).\frac{9}{14}+1.\left(-\frac{5}{7}\right)=-\frac{1405}{1078}\)

b) \(\frac{12}{19}.\frac{7}{15}.\frac{-13}{17}.\frac{19}{12}.\frac{17}{13}=-\frac{7}{15}\)

\(=\left(\frac{12}{19}.\frac{19}{12}\right).\left(-\frac{13}{17}.\frac{17}{13}\right).\frac{7}{15}\)

\(=1.\left(-1\right).\frac{7}{15}\)

\(=-\frac{7}{15}\)

Vậy :