Tính hợp lí: 10/17 -5/13+7/17-8/13

* Hướng dẫn giải

$\begin{array}{l}a)\frac{10}{17}-\frac{5}{13}+\frac{7}{17}-\frac{8}{13}\\ \\ =\left(\frac{10}{17}+\frac{7}{17}\right)+\left(\frac{-5}{13}+\frac{-8}{13}\right)=0\end{array}$

$\begin{array}{l}b)\frac{30}{51}-\frac{20}{52}+\frac{14}{34}-\frac{56}{91}-2\\ \\ =\frac{10}{17}-\frac{5}{13}+\frac{7}{17}-\frac{8}{13}-2=-2\\ \\ c)\frac{-10}{3}+\frac{13}{10}-\frac{1}{6}+\frac{7}{10}\\ \\ =\left(\frac{13}{10}+\frac{7}{10}\right)+\left(\frac{-10}{3}+\frac{-1}{6}\right)\\ \\ =2-\frac{7}{2}=\frac{-3}{2}\\ \\ d)1-\frac{20}{6}+\frac{39}{30}-\frac{4}{24}+\frac{4}{24}\\ \\ =1-\frac{10}{3}+\frac{13}{10}-\frac{1}{6}+\frac{7}{10}=\frac{-1}{2}\end{array}$