\(\frac{1}{2}\)+\(\frac{1}{14}\)+\(\frac...">
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\(c=\frac{1}{2}+\frac{1}{14}+\frac{1}{35}+\frac{1}{65}+\frac{1}{104}+\frac{1}{152}\)

\(c=\frac{1}{2+14+35+65+104+125}\)

\(c=\frac{1}{16+100+229}\)

\(c=\frac{1}{116+229}\)

\(c=\frac{1}{345}\)

29 tháng 3 2019

ai dạy cho cậu vậy

28 tháng 6 2016

353/1995

15 tháng 4 2019

\(A=\frac{1}{2}+\frac{1}{14}+\frac{1}{35}+\frac{1}{65}+\frac{1}{104}+\frac{1}{152}\)

\(A=\frac{1}{1.2}+\frac{1}{2.7}+\frac{1}{7.5}+\frac{1}{5.13}+\frac{1}{13.8}+\frac{1}{8.19}\)

\(A=\frac{2}{1.4}+\frac{2}{4.7}+\frac{2}{7.10}+\frac{2}{10.13}+\frac{2}{13.16}+\frac{2}{16.19}\)

\(A=\frac{2}{3}.\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+\frac{3}{10.13}+\frac{3}{13.16}+\frac{3}{16.19}\right)\)

\(A=\frac{2}{3}.\left(\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16}+\frac{1}{16}-\frac{1}{19}\right)\)

\(A=\frac{2}{3}.\left(1-\frac{1}{19}\right)\)

\(A=\frac{2}{3}.\frac{18}{19}\)

\(\Rightarrow A=\frac{12}{19}\)

15 tháng 4 2019

\(A=\frac{1}{2}+\frac{1}{14}+\frac{1}{35}+\frac{1}{104}+\frac{1}{152}\)

\(A=\frac{2}{4}+\frac{2}{28}+\frac{2}{70}+\frac{2}{130}+\frac{2}{208}+\frac{2}{304}\)

\(A=\frac{2}{1.4}+\frac{2}{4.7}+\frac{2}{7.10}+\frac{2}{10.13}+\frac{2}{13.16}+\frac{2}{16.19}\)

\(A=\frac{2}{3}.\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+\frac{3}{10.13}+\frac{3}{13.16}+\frac{3}{16.19}\right)\)

\(A=\frac{2}{3}.\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16}+\frac{1}{16}-\frac{1}{19}\right)\)

\(A=\frac{2}{3}.\left(1-\frac{1}{19}\right)\)

\(A=\frac{2}{3}.\frac{18}{19}\)

\(A=\frac{12}{19}\)

12 tháng 8 2018

A = \(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{56}\)

\(=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{7.8}\)

  \(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{7}-\frac{1}{8}\)

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

B = \(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{11.13}\)

  \(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{11}-\frac{1}{13}\)

  \(=1-\frac{1}{13}=\frac{12}{13}\)

19 tháng 3 2019

\(A=\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{56}\)

\(=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{7.8}\)

\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{7}-\frac{1}{8}\)

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

\(B=\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{11.13}\)

\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{11}-\frac{1}{13}\)

\(=1-\frac{1}{13}=\frac{12}{13}\)

25 tháng 7 2017

bạn ơi tách ra thừa số chung rồi làm như bình thường nha 

9 tháng 4 2018

1, A=\(\left(1+1+1+1\right)\)-\(\left(\frac{1}{3}+\frac{1}{15}+\frac{1}{35}+\frac{1}{63}\right)\)

     =4-\(\left(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}\right)\)

     = 4-\(\left(\frac{1}{1}-\frac{1}{3}+...+\frac{1}{7}-\frac{1}{9}\right)\)

    =4-\(\left(1-\frac{1}{9}\right)\)

     = 4-\(\frac{8}{9}\)

      = \(\frac{7}{9}\)

25 tháng 4 2017

Ta có:

\(A=\frac{1}{101}+\frac{1}{102}+\frac{1}{103}+...+\frac{1}{200}>\frac{1}{200}+\frac{1}{200}+...+\frac{1}{200}=\frac{100}{200}=\frac{1}{2}\)

\(\Rightarrow A=\frac{1}{101}+\frac{1}{102}+\frac{1}{103}+...+\frac{1}{200}>\frac{1}{2}\)

29 tháng 7 2017

a, \(\frac{14}{25}=\frac{70}{125}\)\(\frac{5}{7}=\frac{70}{98}\)

Mà \(\frac{70}{125}< \frac{70}{98}\)=> \(\frac{14}{25}< \frac{5}{7}\)

b, \(\frac{13}{60}=\frac{65}{300};\frac{27}{100}=\frac{81}{300}\)

Mà \(\frac{65}{300}< \frac{81}{300}\Rightarrow\frac{13}{60}< \frac{27}{100}\)

c, \(1-\frac{2014}{2016}=\frac{2}{2016};1-\frac{998}{1000}=\frac{2}{1000}\)

Mà \(\frac{2}{2016}>\frac{2}{1000}\Rightarrow\frac{2014}{2016}>\frac{998}{1000}\)

d, \(\frac{47}{15}=\frac{329}{105},\frac{65}{21}=\frac{325}{105}\)

Mà \(\frac{329}{105}>\frac{325}{105}\Rightarrow\frac{47}{15}>\frac{65}{21}\)

e, \(\frac{3}{8}=\frac{147}{392},\frac{13}{49}=\frac{104}{392}\)

Mà \(\frac{147}{392}>\frac{104}{392}\Rightarrow\frac{3}{8}>\frac{13}{49}\)

g, \(\frac{43}{49}=\frac{215}{245},\frac{31}{35}=\frac{217}{245}\)

Mà \(\frac{215}{245}< \frac{217}{245}\Rightarrow\frac{43}{49}< \frac{31}{35}\)

f, \(\frac{43}{47}=\frac{1505}{1645},\frac{29}{35}=\frac{1363}{1645}\)

Mà \(\frac{1505}{1645}>\frac{1363}{1645}\Rightarrow\frac{43}{47}>\frac{29}{35}\)

29 tháng 7 2017

mik làm ra kq luôn nha

a)14/25<5/7

b)13/60<27/100

c)2014/2016>998/1000

d)47/15>65/21

e)3/8>13/49

g)43/49<31/35

f)43/47>29/35

k cho mik nha