a,

\(\left(\dfrac{-2}{3}+\dfrac{3}{7}\right):\dfrac{4}{5}+\left(-\dfrac{1}{3}+\dfrac{4}{7}\right):\dfrac{4}{5}\)

\(=\left(\dfrac{-2}{3}+\dfrac{-1}{3}+\dfrac{3}{7}+\dfrac{4}{7}\right):\dfrac{4}{5}\)

\(=\left(-1+1\right):\dfrac{4}{5}=0\)

b,

a) \(\left(-\dfrac{2}{3}+\dfrac{3}{7}\right):\dfrac{4}{5}+\left(-\dfrac{1}{3}+\dfrac{4}{7}\right):\dfrac{4}{5}\)

= \(\left(-\dfrac{2}{3}+\dfrac{3}{7}-\dfrac{1}{3}+\dfrac{4}{7}\right):\dfrac{4}{5}\)

= \(0:\dfrac{4}{5}\)

= 0

b) \(\dfrac{5}{9}\left(\dfrac{1}{11}-\dfrac{5}{22}\right)+\dfrac{5}{9}\left(\dfrac{1}{15}-\dfrac{2}{3}\right)\)

= \(\dfrac{5}{9}:\left(\dfrac{1}{11}-\dfrac{5}{22}+\dfrac{1}{15}-\dfrac{2}{3}\right)\)

= \(\dfrac{5}{9}:-\dfrac{81}{110}\)

= \(-\dfrac{550}{729}\)

Giải:

a) \(\left(\dfrac{-2}{3}+\dfrac{3}{7}\right):\dfrac{4}{5}+\left(\dfrac{-1}{3}+\dfrac{4}{7}\right):\dfrac{4}{5}\)

\(=\left[\left(\dfrac{-2}{3}+\dfrac{2}{7}\right)+\left(\dfrac{-1}{3}+\dfrac{4}{7}\right)\right]:\dfrac{4}{5}\)

\(=\left(\dfrac{-2}{3}+\dfrac{2}{7}-\dfrac{1}{3}+\dfrac{4}{7}\right):\dfrac{4}{5}\)

\(=\left(-1+1\right):\dfrac{4}{5}\)

\(=0:\dfrac{4}{5}\)

\(=0.\dfrac{4}{5}\)

\(=0\)

b) \(\dfrac{5}{9}:\left(\dfrac{1}{11}-\dfrac{5}{22}\right)+\dfrac{5}{9}:\left(\dfrac{1}{15}-\dfrac{2}{3}\right)\)

\(=\dfrac{5}{9}:\left(\dfrac{2}{22}-\dfrac{5}{22}\right)+\dfrac{5}{9}:\left(\dfrac{1}{15}-\dfrac{10}{15}\right)\)

\(=\dfrac{5}{9}:\dfrac{-3}{22}+\dfrac{5}{9}:\dfrac{-3}{5}\)

\(=\dfrac{5}{9}:\left(\dfrac{-3}{22}-\dfrac{3}{5}\right)\)

\(=\dfrac{5}{9}:\left(\dfrac{-3}{22}-\dfrac{3}{5}\right)\)

\(=\dfrac{5}{9}:\dfrac{-81}{110}\)

\(=-\dfrac{550}{729}\)

Chúc bạn học tốt!!!

bài nào bạn

mình sẽ giải toan giúp cậu

b )Với a/b dương 

a/b < a + 1 /b + 1 ( công thức có thể tự chứng minh bằng quy đồng )

Vs a/b âm 

a/b > a + 1/b+1

đề là so sánh hả bạn

uh bạn

khó quá mình chưa làm đc

Độ dài hai cạnh của 1 tam giác bằng 6cm và 2cm tính độ dài còn lại bt rằng số đo cảu nó theo cm là số tự nhiên chẵn