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21 tháng 3 2017

a,\(\frac{4}{3}\)\(\frac{9}{8}\)\(\frac{16}{15}\)\(\frac{25}{24}\)

\(\frac{5}{3}\)

b, \(\frac{4}{3}\)\(\frac{9}{8}\)\(\frac{16}{15}\)\(\frac{25}{24}\)\(\frac{36}{35}\)\(\frac{49}{48}\)\(\frac{64}{63}\)\(\frac{81}{80}\)

\(\frac{9}{5}\)

1 tháng 3 2022

chi tiết hơn đc k bn

1 tháng 4 2020

\(\frac{3}{4}.\frac{8}{9}.\frac{15}{16}.\frac{24}{25}...\frac{63}{64}\)

\(=\frac{1.3}{2.2}.\frac{2.4}{3.3}.\frac{3.5}{4.4}.\frac{4.6}{5.5}...\frac{7.9}{8.8}\)

\(=\frac{1.3.2.4.3.5.4.6...7.9}{2.2.3.3.4.4.5.5...8.8}\)

\(=\frac{1.9}{2.8}=\frac{9}{16}\)

25 tháng 3 2018

\(\frac{4}{3}\times\frac{9}{8}\times...\times\frac{81}{80}=\frac{2^2}{1\times3}\times\frac{3^2}{2\times4}\times...\times\frac{9^2}{8\times10}\)

\(=\frac{2\times3\times4\times...\times9}{1\times2\times3\times...\times8}\times\frac{2\times3\times4\times...\times9}{3\times4\times5\times...\times10}\\ =\frac{9}{1}\times\frac{2}{10}=\frac{9}{5}\)

4/3.9/8.16/15.25/24.36/35.49/48.64/63.81/80

=3/2.16/15.25/24.36/35.49/48.64/63.81/80

=5/3.36/35.49/48.64/63.81/80

=7/4.64/63.81/80

=9/5

+

=(1-1/2)(1+1/2)*...*(1+1/10)(1-1/10)

=1/2*2/3*...*9/10*3/2*4/3*...*11/10

=1/10*11/2

=11/20

21 tháng 9

a; 

c; \(\dfrac{1}{10}\) + \(\dfrac{4}{20}\) + \(\dfrac{9}{30}\)+\(\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)

\(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)

\(\dfrac{1+2+3+4+5+6+7+8+9}{10}\)

=  \(\dfrac{\left(1+9\right)+\left(2+8\right)+\left(3+7\right)+\left(4+6\right)+5}{10}\)

\(\dfrac{10+10+10+10+5}{10}\)

\(\dfrac{\left(10+10+10+10\right)+5}{10}\)

\(\dfrac{10\times4+5}{10}\)

\(\dfrac{45}{10}\)

\(\dfrac{9}{2}\)

9 tháng 8 2016

a) 3/7 + 4/9 + 4/7 + 5/9

= ( 3/7 + 4/7 ) + ( 4/9 + 5/9 )

= 7/7 + 9/9

= 1  + 1 

= 2

b)1/5 + 4/10 + 9/15 + 16/20 + 25/25 + 36/30 + 49/35 + 64/40 + 81/45

= 1/5 + 2/5 + 3/5 + 4/5 + 5/5 + 6/5 + 7/5 + 8/5 + 9/5

= ( 1/5 + 9/5 ) + ( 2/5 + 8/5 ) + (7/5 + 3/5 ) + ( 4/5 + 6/5  ) + 5/5

= 2 + 2 + 2 + 2 + 1

= 2  x 4 + 1

= 8  +1 

= 9

c)  1/8 + 1/12 + 3/8 + 5/12

= ( 1/8 + 3/8 ) + ( 1/12 + 5/12)

= 4/8 + 6/12

= 1/2 + 1/2

= 2/4 = 1/2

mỏi tay rồi

22 tháng 9

d; (1 - \(\dfrac{1}{2}\)) x (1 - \(\dfrac{1}{3}\)) x (1 - \(\dfrac{1}{4}\)) x ... x ( 1 - \(\dfrac{1}{100}\))

 = \(\dfrac{1}{2}\) x \(\dfrac{2}{3}\)  x \(\dfrac{3}{4}\) x \(\dfrac{3}{4}\) x ... x \(\dfrac{99}{100}\)

\(\dfrac{1}{100}\)