e) 18/13-3/8+8/13-5/8

=26/13-8/8

=2-1

=1

f) (157/8.(12/7)-53/4.(12/7)).4/5

=12/7(157/8-106/8).4/5

=306/35

,\(49\frac{8}{23}-\left(5\frac{7}{32}+14\frac{8}{23}\right)\)

\(49\frac{8}{23}-14\frac{8}{23}-5\frac{7}{32}=29\frac{25}{32}\)

\(71\frac{38}{45}-\left(43\frac{38}{45}-1\frac{17}{57}\right)\)

\(71\frac{38}{45}-43\frac{38}{45}+1\frac{17}{57}\)

\(28+1\frac{17}{57}=29\frac{17}{57}\)

(0,6+0,415-0,015).8/3.0,25=8/3.0,25=2/3

5/6.1/8-(9/4-0,6)10/11

=5/48-(9/4-3/5).10/11

=5/48-3/2

=(5-72)/48=-67/48

(1/8).4/3-2/7.12,25

=1/6-7/2=-10/3

\(\left(\frac{7}{8}-\frac{3}{4}\right)\cdot1\frac{1}{3}-\frac{2}{7}\cdot\left(3,5\right)^2\)\(=\frac{1}{8}\cdot\frac{4}{3}-\frac{2}{7}\cdot12,25\)\(=\frac{1}{6}-3,5=\frac{1}{6}-\frac{7}{5}=\frac{-37}{30}\)

A = 2/3² + 2/5²  + 2/7² +.....+ 2/2021²  = 2 ( 2/3² + 2/5²  + 2/7² +.....+ 2/2021² )

Đặt A₁ = 2/3² + 2/5²  + 2/7² +.....+ 2/2021²

1/3² < 1/3² - 1 = 1/2.4 = 1/2 ( 1/2 - 1/4 ) 

 1/5²  < 1/5²  - 1 = 1/4.6 = 1/2 ( 1/4 - 1/6 ) 

 2/2021² < 1/2021² - 1 = 1/ 2020.2022 = 1/2 ( 1/2020 - 1/2022 )

A₁ < 1/2 ( 1/2 - 1/4 + 1/4 - 1/6 + 1/2020 - 1/2022 ) 

A₁ < 1/2 ( 1/2 - 1/2022 ) = 1/2.1010/2022 

2A₁ <  2.1/2.1010/2022 nên A = 2A₁ < 1010/2022 

Vậy A < 1010/2022

\(6\frac{5}{12}:2\frac{3}{4}+11\frac{1}{4}.\left(\frac{1}{3}-\frac{1}{5}\right)=\frac{77}{12}:\frac{11}{4}+\frac{45}{4}.\frac{2}{15}=\frac{7}{3}+\frac{3}{2}=\frac{23}{6}\)

<=>77/12:11/3+45/4(2/15)

=7/4+3/2=13/4

có vẻ liên quan đến tin học với toán

mk tính bằng=-13/5

\(5-2\left(-\frac{1}{2}\right)^2=5-2\cdot\frac{1}{4}=5-\frac{1}{2}=\frac{9}{2}\)

\(5-2\left(-\frac{1}{2}\right)^2=5-2.\frac{1}{4}=5-\frac{1}{2}=\frac{9}{2}\)\(\frac{9}{2}\)

\(\left(2-\frac{1}{2}\right).\left(-\frac{3}{4}+\frac{1}{2}\right)=\frac{1}{2}.\frac{-1}{4}=\frac{-1}{8}\)

\(\left(\frac{3}{8}+\frac{-3}{4}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}=\left(\frac{-3}{8}+\frac{7}{12}\right).\frac{6}{5}+\frac{1}{2}=\frac{5}{24}.\frac{6}{5}+\frac{1}{2}=\frac{1}{4}+\frac{2}{4}=\frac{3}{4}\)

\(\frac{1}{2}+\frac{3}{4}-\left(\frac{3}{4}-\frac{4}{5}\right)=\frac{2}{4}+\frac{3}{4}-\left(-\frac{1}{20}\right)=\frac{5}{4}+\frac{1}{20}=\frac{25}{20}+\frac{1}{20}=\frac{26}{20}=\frac{13}{10}\)