Tính hợp lý a) -17/13 + (25/101 + 4/13) b) (-5/12 + 6/11) + (7/17

* Hướng dẫn giải

a) 

$\begin{array}{l}\frac{-17}{13}+\left(\frac{25}{101}+\frac{4}{13}\right)\\ =\frac{-17}{13}+\frac{25}{101}+\frac{4}{13}\\ =\left(\frac{-17}{13}+\frac{4}{13}\right)+\frac{25}{101}\\ =-1+\frac{25}{101}=\frac{-76}{101}\end{array}$

b)

$\begin{array}{l}\left(\frac{-5}{12}+\frac{6}{11}\right)+\left(\frac{7}{17}+\frac{5}{11}+\frac{5}{12}\right)\\ =\frac{-5}{12}+\frac{6}{11}+\frac{7}{17}+\frac{5}{11}+\frac{5}{12}\\ =\left(\frac{-5}{12}+\frac{5}{12}\right)+\left(\frac{6}{11}+\frac{5}{11}\right)+\frac{7}{17}\\ =0+1+\frac{7}{17}=1\frac{7}{17}\end{array}$