Cho E=( -3/31+ -6/17 +1/25) + (-28/31 + -11/17 + -1/5) . Chọn câu đúng

* Hướng dẫn giải

Đáp án cần chọn là: B

$\begin{array}{l}\\ \begin{array}{l}E=\left(\frac{-3}{31}+\frac{-6}{17}+\frac{1}{25}\right)+\left(\frac{-28}{31}+\frac{-11}{17}+\frac{-1}{5}\right)\\ E=\frac{-3}{31}+\frac{-6}{17}+\frac{1}{25}+\frac{-28}{31}+\frac{-11}{17}+\frac{-1}{5}\\ E=\left(\frac{-3}{31}+\frac{-28}{31}\right)+\left(\frac{-6}{17}+\frac{-11}{17}\right)+\left(\frac{1}{25}+\frac{-1}{5}\right)\\ E=-1-1-\frac{4}{25}\\ E=\frac{-54}{25}\end{array}\end{array}$