Question

Bài 6 : Thực hiện phép tính

a) -1/21+ -1/28 - -1/21 - 3/14

b) (-1/5 + 3/12) + -3/4

c) -4/11.2/5 + 6/11. -3/10

Nhân là dấu chấm nha!

Answer 1

Answer 2

a) \(\frac{-1}{21}+\frac{-1}{28}-\frac{-1}{21}-\frac{3}{14}\)

\(=\frac{-1}{21}+\frac{-1}{28}+\frac{1}{21}+\frac{-3}{14}\)

\(=\left(\frac{-1}{21}+\frac{1}{21}\right)+\left(\frac{-1}{28}+\frac{-3}{14}\right)\)

\(=0+\left(\frac{-1}{28}+\frac{-6}{28}\right)\)

\(=0+\frac{-1}{4}=\frac{-1}{4}\)

b) \(\left(\frac{-1}{5}+\frac{3}{12}\right)+\frac{-3}{4}\)

\(=\frac{-1}{5}+\frac{1}{4}+\frac{-3}{4}\)

\(=\left(\frac{1}{4}+\frac{-3}{4}\right)+\frac{-1}{5}\)

\(=\frac{-1}{2}+\frac{-1}{5}\)

\(=\frac{-5}{10}+\frac{-2}{10}=\frac{-7}{10}\)

c) \(\frac{-4}{11}\cdot\frac{2}{5}+\frac{6}{11}\cdot\frac{-3}{10}\)

\(=\frac{-8}{55}+\frac{-9}{55}=\frac{-17}{55}\)