Question

Tính giải trị của biểu thức 

A = -2/5 + ( -2/5 + 2)

B = ( -5/24 + 0,75 + 7/12 ) : -17/8

C = 3/7 + ( - 1/5 + -3/7)

D = ( 6 - 14/5 ). 25/8 - 8/5 : 1/4

 

Answer 1

A = - 2 / 5 + ( - 2 / 5 + 2 )

A = - 2 / 5 + 8 / 5

A = 6 / 5

B = ( - 5 / 24 + 0, 75 + 7 / 12 ) : - 17/8

B = 9 / 8 : - 17/8

B = -9 / 17

C = 3 / 7 + ( - 1 / 5 + - 3 / 7 )

C = 3 / 7 - 1 / 5 - 3 / 7 

C = - 1 / 5 

D = ( 6 - 14 / 5 ) . 25 / 8 - 8 / 5 : 1 / 4 

D = 16 / 5 . 25 / 8 - 8 / 5 . 4 

D = 10 - 6 , 4 

D = 3,6

Answer 2

\(A=-\frac{2}{5}+\left[\left(-\frac{2}{5}\right)+2\right]=\left[\left(-\frac{2}{5}\right)+\left(-\frac{2}{5}\right)\right]+2=\left(-\frac{4}{5}\right)+2=\left(-\frac{4}{5}\right)+\frac{10}{5}=\frac{6}{5}\)\(\frac{10}{5}=\frac{6}{5}\)

\(B=\left[\left(-\frac{5}{24}\right)+0,75+\frac{7}{12}\right]:\left(\frac{-17}{8}\right)\)\(=\left[\left(-\frac{5}{24}\right)+\frac{3}{4}+\frac{7}{12}\right].\frac{-8}{17}\)

   \(=\left[\left(-\frac{5}{24}\right)+\frac{18}{24}+\frac{14}{24}\right].\frac{-8}{17}\)\(=\frac{27}{24}.\frac{-8}{17}=\frac{9}{8}.\frac{-8}{17}=\frac{9.\left(-8\right)}{8.17}=\frac{-9}{17}\)

\(C=\frac{3}{7}+\left[\left(-\frac{1}{5}\right)+\left(-\frac{3}{7}\right)\right]=\left[\frac{3}{7}+\left(-\frac{3}{7}\right)\right]+\left(-\frac{1}{5}\right)=-\frac{1}{5}\)

\(D=\left(6-\frac{14}{5}\right).\frac{25}{8}-\frac{8}{5}:\frac{1}{4}=\left(\frac{30}{5}-\frac{14}{5}\right).\frac{25}{8}-\frac{8}{5}.4\)

\(=\frac{16}{5}.\frac{25}{8}-\frac{32}{5}=\frac{16.25}{5.8}-\frac{32}{5}=10-\frac{32}{5}\)\(=\frac{50}{5}-\frac{32}{5}=\frac{18}{5}\)