\(\dfrac{-4}{9}.\dfrac{7}{15}+\dfrac{4}{-9}.\dfrac{8}{15}\)

=\(\dfrac{-4}{9}.\left(\dfrac{7}{15}+\dfrac{8}{15}\right)\)

=\(\dfrac{-4}{9}.1\)=\(\dfrac{-4}{9}\)

\(\dfrac{-4}{9}.\dfrac{7}{15}+\dfrac{4}{-9}.\dfrac{8}{15}\) 

\(=\dfrac{-4}{9}.\dfrac{7}{15}+\dfrac{-4}{9}.\dfrac{8}{15}\) 

\(=\dfrac{-4}{9}.\left(\dfrac{7}{15}+\dfrac{8}{15}\right)\) 

\(=\dfrac{-4}{9}.1\) 

\(=\dfrac{-4}{9}\)

=19/18 nha bn

học tốt

=19/18 nha bn

học tốt

\(\frac{4}{9}\cdot\frac{7}{15}+\frac{31}{30}\cdot\frac{11}{18}+\frac{4}{9}\cdot\frac{8}{15}-\frac{11}{18}\cdot\frac{1}{30}\)

\(=\frac{4}{9}.\left(\frac{7}{15}+\frac{8}{15}\right)+\frac{11}{18}.\left(\frac{31}{30}-\frac{1}{30}\right)\)

\(=\frac{4}{9}+\frac{11}{18}=\frac{8}{18}+\frac{11}{18}=\frac{19}{18}\)

a; -\(\dfrac{4}{9}.\dfrac{7}{15}+\dfrac{4}{-9}.\dfrac{8}{15}\)

= - \(\dfrac{4}{9}\).(\(\dfrac{7}{15}+\dfrac{8}{15}\))

= - \(\dfrac{4}{9}\).1

= - \(\dfrac{4}{9}\)

b; - \(\dfrac{5}{4}.\dfrac{16}{25}\) + \(\dfrac{-5}{4}\).\(\dfrac{9}{25}\)

= - \(\dfrac{5}{4}\).(\(\dfrac{16}{25}\) + \(\dfrac{9}{25}\))

= - \(\dfrac{5}{4}\). 1

= - \(\dfrac{5}{4}\)

c; \(-\dfrac{5}{12}.\dfrac{4}{19}\) + \(\dfrac{-7}{12}.\dfrac{4}{19}-\dfrac{40}{57}\)

= - \(\dfrac{5}{12}\).\(\dfrac{4}{19}\) - \(\dfrac{7}{12}\).\(\dfrac{4}{19}\) - \(\dfrac{4}{19}\).\(\dfrac{10}{3}\)

= - \(\dfrac{4}{19}\).(\(\dfrac{5}{12}\) + \(\dfrac{7}{12}\) + \(\dfrac{10}{3}\))

= - \(\dfrac{4}{19}\).\(\dfrac{13}{3}\)

= - \(\dfrac{52}{57}\)

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

Chốc nữa mình lm tp nha

Lâu quá nên mình làm xong hết rồi !

\(\dfrac{5}{-4}.\dfrac{16}{25}+\dfrac{4}{-9}.\dfrac{8}{15}=-\dfrac{4}{5}+\left(-\dfrac{32}{135}\right)=-\dfrac{28}{27}\)

\(\dfrac{5}{-4}.\dfrac{16}{25}+\dfrac{4}{-9}.\dfrac{8}{15}=\dfrac{-4}{5}+\dfrac{-32}{135}=\dfrac{-28}{27}\)