Question

Thực hiện phép tính (Hợp lí nếu có thể):

a) \(\dfrac{-2}{5}.\dfrac{4}{11}+0,4.\dfrac{-6}{11}-\dfrac{1}{11}:\dfrac{5}{2}\)

b)\(\dfrac{-23}{17}-\dfrac{5}{39}-\left(\dfrac{-6}{17}+\dfrac{34}{39}\right)+2,54\)

 

Answer 1

a: \(-\dfrac{2}{5}\cdot\dfrac{4}{11}+0,4\cdot\dfrac{-6}{11}-\dfrac{1}{11}:\dfrac{5}{2}\)

\(=-\dfrac{2}{5}\cdot\dfrac{4}{11}+\dfrac{2}{5}\cdot\dfrac{-6}{11}-\dfrac{1}{11}\cdot\dfrac{2}{5}\)

\(=\dfrac{2}{5}\left(-\dfrac{4}{11}-\dfrac{6}{11}-\dfrac{1}{11}\right)\)

\(=\dfrac{2}{5}\cdot\dfrac{-11}{11}=-\dfrac{2}{5}\)

b: \(-\dfrac{23}{17}-\dfrac{5}{39}-\left(-\dfrac{6}{17}+\dfrac{34}{39}\right)+2,54\)

\(=-\dfrac{23}{17}-\dfrac{5}{39}+\dfrac{6}{17}-\dfrac{34}{39}+2,54\)

\(=\left(-\dfrac{23}{17}+\dfrac{6}{17}\right)+\left(-\dfrac{5}{39}-\dfrac{34}{39}\right)+2,54\)

\(=-\dfrac{17}{17}-\dfrac{39}{39}+2,54=2,54-2=0,54\)