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DT
19 tháng 8 2023

\(\left(1-\dfrac{1}{2}\right)\times\left(1-\dfrac{1}{3}\right)\times\left(1-\dfrac{1}{4}\right)\times...\times\left(1-\dfrac{1}{2023}\right)\\ =\dfrac{1}{2}\times\dfrac{2}{3}\times\dfrac{3}{4}\times...\times\dfrac{2022}{2023}\\ =\dfrac{1}{2023}\)

19 tháng 8 2023

đáp án B bạn nha 

1) Ta có: \(\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{7}{25}\cdot\dfrac{5}{7}\right)\)

\(=\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{1}{5}\right)\)

=0

2) Ta có: \(\dfrac{8}{17}\cdot\dfrac{4}{15}+\dfrac{8}{17}\cdot\dfrac{22}{15}-\dfrac{8}{15}\cdot\dfrac{9}{17}\)

\(=\dfrac{8}{17}\left(\dfrac{4}{15}+\dfrac{22}{15}-\dfrac{9}{15}\right)\)

\(=\dfrac{8}{17}\cdot\dfrac{15}{15}=\dfrac{8}{17}\)

3) Ta có: \(\dfrac{2021}{2}\cdot\dfrac{1}{3}+\dfrac{4042}{4}\cdot\dfrac{1}{5}+\dfrac{6063}{3}\cdot\dfrac{22}{15}\)

\(=\dfrac{2021}{2}\left(\dfrac{1}{3}+\dfrac{1}{5}\right)+2021\cdot\dfrac{22}{15}\)

\(=\dfrac{2021}{2}\cdot\dfrac{8}{15}+\dfrac{2021}{2}\cdot\dfrac{44}{15}\)

\(=\dfrac{2021}{2}\cdot\dfrac{52}{15}\)

\(=\dfrac{52546}{15}\)

4) Ta có: \(\dfrac{4}{7}\cdot\dfrac{2}{13}+\dfrac{8}{13}:\dfrac{7}{4}+\dfrac{4}{7}:\dfrac{13}{2}+\dfrac{4}{7}\cdot\dfrac{1}{13}\)

\(=\dfrac{4}{7}\left(\dfrac{2}{13}+\dfrac{8}{13}+\dfrac{2}{13}+\dfrac{1}{13}\right)\)

\(=\dfrac{4}{7}\)

2 tháng 7 2021

cảm ơn nhé

vui

13 tháng 6 2020

\(\left(1-\frac{1}{2018}\right)\times\left(1-\frac{1}{2019}\right)\times\left(1-\frac{1}{2020}\right)\times\left(1-\frac{1}{2021}\right)\times\left(1-\frac{1}{2022}\right)\)

\(=\frac{2017}{2018}\times\frac{2018}{2019}\times\frac{2019}{2020}\times\frac{2020}{2021}\times\frac{2021}{2022}\)

\(=\frac{2017}{2022}\)

x +\(\frac{1}{6}\)=\(\frac{1}{3}\)-\(\frac{1}{4}\)

x +\(\frac{1}{6}\)=\(\frac{1}{12}\)

x            =\(\frac{1}{12}\)-\(\frac{1}{6}\)

x            =\(-\frac{1}{12}\)

x -\(\frac{5}{12}\)=\(\frac{1}{3}+\frac{1}{4}\)

x -\(\frac{5}{12}\)=\(\frac{7}{12}\)

x             =\(\frac{7}{12}\)+\(\frac{5}{12}\)

x             = 1

x +\(\frac{1}{2}\)=\(\frac{4}{5}\)

x             =\(\frac{4}{5}\)-\(\frac{1}{2}\)

x             =\(\frac{3}{10}\)

x -\(\frac{1}{6}\)=\(\frac{1}{2}\)+\(\frac{1}{3}\)

x -\(\frac{1}{6}\)=\(\frac{5}{6}\)

x            =\(\frac{5}{6}\)+\(\frac{1}{6}\)

x            = 1

x +\(\frac{1}{8}\)=\(\frac{1}{2}\)-\(\frac{1}{3}\)

x +\(\frac{1}{8}\)=\(\frac{1}{6}\)

x             =\(\frac{1}{6}\)-\(\frac{1}{8}\)

x             =\(\frac{1}{24}\)

Học tốt!!!

help mik với

1 tháng 4 2022

\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{98}-\dfrac{1}{99}\)

\(=1-\dfrac{1}{99}=\dfrac{98}{99}\)

14 tháng 4 2017

Gửi kết bn với mh nhé!

14 tháng 4 2017

ban ko tra loi ho minh cau nay a 

neu the minh ket ban kieu gi

5 tháng 3 2018

22/7

7/5

43/4

15/28

1/42

7/12

1/4

2/5

5/12

7 tháng 6 2016

\(\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)\left(1-\frac{1}{4}\right)\)\(\frac{2-1}{2}.\frac{3-1}{3}.\frac{4-1}{4}\)\(\frac{1}{2}.\frac{2}{3}.\frac{3}{4}\)\(\frac{1.2.3}{2.3.4}=\frac{1}{4}\)

\(\left(1+\frac{1}{2}\right):\left(1+\frac{1}{3}\right):\left(1+\frac{1}{4}\right)\)\(\frac{2+1}{2}:\frac{3+1}{3}:\frac{4+1}{4}\)\(\frac{3}{2}:\frac{4}{3}:\frac{5}{4}=\frac{3}{2}.\frac{3}{4}.\frac{4}{5}=\frac{3.3.4}{2.4.5}=\frac{3.3}{2.5}=\frac{9}{10}\)

\(\frac{6}{5}-\frac{4}{5}.\frac{4}{8}+1=\frac{6}{5}+1-\frac{4.4}{5.8}=\frac{6+5}{5}-\frac{4}{5.2}=\frac{11}{5}-\frac{2}{5}=\frac{9}{5}\)
x < \(\frac{3}{4}+\frac{4}{5}=\frac{15}{20}+\frac{16}{20}=\frac{31}{20}=\frac{20}{20}+\frac{11}{20}=1\frac{11}{20}\)=> x = 0 ; 1

\(\frac{1}{2}+\frac{2}{3}< x< 4-\frac{5}{4}\)<=> \(\frac{3}{6}+\frac{4}{6}< x< \frac{16}{4}-\frac{5}{4}\)<=> \(\frac{7}{6}< x< \frac{11}{4}\)=> \(\frac{14}{12}< \frac{12x}{12}< \frac{33}{12}\)

=> 14 < 12x < 33 => 12x = 24 => x = 24 : 12 = 2

2 tháng 5 2016

Bài 1

1/2 x 3/4 : 4/5 

= 3/8 : 4/5 

= 3/8 x 5/4

= 15/32

2/3 + 1/6 - 1/2

= 4/6 + 1/6 - 3/6

= 5/6 - 3/6

= 1/3

3/5 + 4 : 2/3 - 3/2

= 3/5 + 4 x 3/2 - 3/2

= 3/5 + 6 - 3/2

= 3/5 + 30/5 - 3/2

= 33/5 - 3/2

= 66/10 - 15/10

= 28/5

Bài 2

x - 1/4 = 1/2 

x         = 1/2 + 1/4

x         = 2/4 + 1/4 

x         = 3/4

2/3 + x = 1

         x = 1 - 2/3 

         x = 3/3 - 2/3

         x = 1/3

2 tháng 5 2016

1/2 x 3/4 : 4/5

=1/2 x 3/4 x 4/5

=3/8 x 4/5

=3/10

11 tháng 3 2022

(2/3 x 4/5) x 5/6

=   8/15     x 5/6

=             4/9

(2/3 x 4/5) x 5/6 

= (5/6 x 4/5) x 2/3

=        2/3     x 2/3

=              4/9

(1/2 + 1/3) x 1/5

=   5/6        x 1/5

=               1/6

(1/2 + 1/3) x 1/5

= (1/2 x 1/5) + (1/3 x 1/5)

=       1/10    +        1/15

=                 1/6

4A6?

11 tháng 3 2022

undefinedĐây bạn nhé