tính
-4/9.7/15+4/-9.8/15
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\(\dfrac{-4}{9}.\dfrac{7}{15}+\dfrac{4}{-9}.\dfrac{8}{15}\)
=\(\dfrac{-4}{9}.\left(\dfrac{7}{15}+\dfrac{8}{15}\right)\)
=\(\dfrac{-4}{9}.1\)=\(\dfrac{-4}{9}\)
\(\dfrac{-4}{9}.\dfrac{7}{15}+\dfrac{4}{-9}.\dfrac{8}{15}\)
\(=\dfrac{-4}{9}.\dfrac{7}{15}+\dfrac{-4}{9}.\dfrac{8}{15}\)
\(=\dfrac{-4}{9}.\left(\dfrac{7}{15}+\dfrac{8}{15}\right)\)
\(=\dfrac{-4}{9}.1\)
\(=\dfrac{-4}{9}\)
Bài 1
a, A=5/12.6/11+5/12.5/11+7/12
A=5/12x(6/11+5/11)+7/12
A=5/12x1+7/12
A=12/12=1
\(\dfrac{5}{-4}.\dfrac{16}{25}+\dfrac{4}{-9}.\dfrac{8}{15}=-\dfrac{4}{5}+\left(-\dfrac{32}{135}\right)=-\dfrac{28}{27}\)
\(\dfrac{5}{-4}.\dfrac{16}{25}+\dfrac{4}{-9}.\dfrac{8}{15}=\dfrac{-4}{5}+\dfrac{-32}{135}=\dfrac{-28}{27}\)
\(\frac{-4}{9}.\frac{7}{15}+\frac{4}{-9}.\frac{8}{15}\)
\(\Rightarrow\frac{-4}{9}.\frac{7}{15}+\frac{-4}{9}.\frac{8}{15}\)
\(\Rightarrow\frac{-4}{9}.\left(\frac{7}{15}+\frac{8}{15}\right)\)
\(\Rightarrow\frac{-4}{9}.\frac{15}{15}\)
\(\Rightarrow\frac{-4}{9}.1\)
\(\Rightarrow\frac{-4}{9}\)
\(\frac{-4}{9}.\frac{7}{15}+\frac{4}{-9}.\frac{8}{15}\)
\(=\frac{-4}{9}.\frac{7}{15}+\frac{-4}{9}.\frac{8}{15}\)
\(=\frac{-4}{9}.\left(\frac{7}{15}+\frac{8}{15}\right)\)
\(=\frac{-4}{9}.\frac{15}{15}\)
\(=\frac{-4}{9}.1\)
\(=\frac{-4}{9}\)