HELP BÀI 5
a)\(\dfrac{1}{3}+\dfrac{2}{5}+\dfrac{4}{3}+\dfrac{3}{5}+\dfrac{7}{3}=\left(\dfrac{1}{3}+\dfrac{4}{3}+\dfrac{7}{3}\right)+\left(\dfrac{2}{5}+\dfrac{3}{5}\right)\)
\(=4+1=5\)
b)\(\dfrac{5}{2}+\dfrac{6}{11}+\dfrac{2}{8}+\dfrac{7}{2}+\dfrac{6}{8}+\dfrac{5}{11}=\left(\dfrac{5}{2}+\dfrac{7}{2}\right)+\left(\dfrac{6}{11}+\dfrac{5}{11}\right)+\left(\dfrac{2}{8}+\dfrac{6}{8}\right)\)
\(=6+1+1=8\)
c)\(\dfrac{-1}{8}+\dfrac{6}{7}+\dfrac{2}{14}+\dfrac{-7}{8}+\dfrac{7}{9}=\dfrac{-1}{8}+\dfrac{6}{7}+\dfrac{1}{7}+\dfrac{-7}{8}+\dfrac{7}{9}\)
\(=\left(\dfrac{-1}{8}+\dfrac{-7}{8}\right)+\left(\dfrac{6}{7}+\dfrac{1}{7}\right)+\dfrac{7}{9}\)
\(=-1+1+\dfrac{7}{9}=\dfrac{7}{9}\)
d)\(\dfrac{-4}{12}+\dfrac{18}{45}+\dfrac{-6}{9}+\dfrac{-21}{35}+\dfrac{6}{30}=\dfrac{-1}{3}+\dfrac{2}{5}+\dfrac{-2}{3}+\dfrac{-3}{5}+\dfrac{1}{5}\)
\(=\left(\dfrac{-1}{3}+\dfrac{-2}{3}\right)+\left(\dfrac{2}{5}+\dfrac{-3}{5}+\dfrac{1}{5}\right)\)
\(=-1+0=-1\)
help bài 3 câu a ,b, và c help