Question

a) \(\dfrac{8}{40}+\dfrac{-36}{45}\)

b) \(\dfrac{3}{5}+\dfrac{4}{-7}\)

c) \(\dfrac{8}{40}+\dfrac{-36}{45}\)

d) \(\dfrac{3}{5}+\dfrac{4}{-7}\)

e) \(\dfrac{4}{9}-\dfrac{-5}{6}\)

f) \(\dfrac{6}{7}+\dfrac{1}{7}.\dfrac{2}{7}+\dfrac{1}{7}.\dfrac{5}{7}\)

g) \(\dfrac{4}{9}.\dfrac{13}{3}-\dfrac{4}{3}.\dfrac{40}{9}\)

h) \(8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)\)

i) \(\left(10\dfrac{2}{9}+2\dfrac{3}{5}\right)-6\dfrac{2}{9}\)

k) \(\dfrac{7}{19}.\dfrac{8}{11}+\dfrac{7}{19}.\dfrac{3}{11}-\dfrac{26}{19}\)

Answer 1

a) \(\dfrac{8}{40}+\dfrac{-36}{45}=\dfrac{1}{5}+\dfrac{-4}{5}=\dfrac{1-4}{5}=-\dfrac{3}{5}\)

b) \(\dfrac{3}{5}+\dfrac{4}{-7}=\dfrac{3}{5}-\dfrac{4}{7}=\dfrac{21-20}{35}=\dfrac{1}{35}\)

c, d) giống a, b.

e) \(\dfrac{4}{9}-\dfrac{-5}{6}=\dfrac{4}{9}+\dfrac{5}{6}=\dfrac{8+15}{18}=\dfrac{23}{18}\)

f) \(\dfrac{6}{7}+\dfrac{1}{7}\cdot\dfrac{2}{7}+\dfrac{1}{7}\cdot\dfrac{5}{7}=\dfrac{6}{7}+\dfrac{2}{49}+\dfrac{5}{49}=1\)

g) \(\dfrac{4}{9}\cdot\dfrac{13}{3}-\dfrac{4}{3}\cdot\dfrac{40}{9}=\dfrac{52}{27}-\dfrac{160}{27}=-4\)

h) \(8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)=\dfrac{16}{7}-\left(\dfrac{4}{3}+\dfrac{8}{7}\right)=\dfrac{16}{7}-\dfrac{52}{21}=-\dfrac{4}{21}\)

i) \(\left(10\dfrac{2}{9}+2\dfrac{3}{5}\right)-6\dfrac{2}{9}=\left(\dfrac{20}{9}+\dfrac{6}{5}\right)-2\cdot\dfrac{2}{3}=\dfrac{154}{45}-\dfrac{4}{3}=\dfrac{94}{45}\)

k) \(\dfrac{7}{19}\cdot\dfrac{8}{11}+\dfrac{7}{19}\cdot\dfrac{3}{11}-\dfrac{26}{19}=\dfrac{56}{209}+\dfrac{21}{209}-\dfrac{26}{19}=-1\)

Answer 2

a)\(\dfrac{8}{40}+\dfrac{-36}{45}=\dfrac{1}{5}+\dfrac{-36}{45}=\dfrac{9}{45}+\dfrac{-36}{45}=\dfrac{-27}{45}\)

b)

\(\dfrac{3}{5}+\dfrac{4}{-7}=\dfrac{3}{5}+\dfrac{-4}{7}=\dfrac{21}{35}+\dfrac{-20}{35}=\dfrac{1}{35}\)

c)\(\dfrac{8}{40}+\dfrac{-36}{45}=\dfrac{1}{5}+\dfrac{-36}{45}=\dfrac{9}{45}+\dfrac{-36}{45}=\dfrac{-27}{45}\)

d)

\(\dfrac{3}{5}+\dfrac{4}{-7}=\dfrac{3}{5}+\dfrac{-4}{7}=\dfrac{21}{35}+\dfrac{-20}{35}=\dfrac{1}{35}\)

(chiều mình làm tiếp!!!)