Cho C=( -1/6 +5/12) + (7/12 +11/24 + -5/6)

* Hướng dẫn giải

Đáp án cần chọn là: D

$\begin{array}{l}C=\left(\frac{-1}{6}+\frac{5}{12}\right)+\left(\frac{7}{12}+\frac{11}{24}+\frac{-5}{6}\right)\\ C=\left(\frac{-1}{6}+\frac{-5}{6}\right)+\left(\frac{5}{12}+\frac{7}{12}\right)+\frac{11}{24}\\ C=-1+1+\frac{11}{24}\\ C=\frac{11}{24}\end{array}$

$\begin{array}{l}D=\left(\frac{-5}{7}+\frac{-2}{7}\right)+\left(\frac{3}{4}+\frac{1}{4}\right)+\left(\frac{-1}{5}+\frac{7}{15}\right)\\ D=-1+1+\frac{4}{15}\\ D=\frac{4}{15}\end{array}$