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Hà Khánh Dung
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Minh Hoàng
7 tháng 4 2018 lúc 21:53

=>A:1/2=1/1x3+1/3x5+1/5x7+...+1/99x101

=>2a=1/2(2/1x3+2/3x5+...+2/99x101)

từ đây tự làm

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Phạm Tuấn Đạt
1 tháng 5 2018 lúc 20:57

\(A=\frac{1}{2.3}+\frac{1}{6.5}+\frac{1}{10.7}+...+\frac{1}{198.101}\)

\(\Rightarrow2A=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{99.101}\)

\(\Rightarrow2A=\frac{1}{2}\left(1-\frac{1}{101}\right)\)

\(\Rightarrow4A=\frac{100}{101}\)

\(\Leftrightarrow A=\frac{100}{101}.\frac{1}{4}=\frac{4.25}{101.4}=25< 26\)

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Yoona SNSD
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dieuduyen
19 tháng 3 2016 lúc 19:18

=\(\frac{1}{1.2.3}+\frac{1}{2.3.4}+............+\frac{1}{18.19.20}\)

=\(\frac{2}{1.2.3.2}+\frac{2}{2.3.4.2}+............+\frac{2}{18.19.20.2}\)

=\(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}............+\frac{1}{18.19}-\frac{1}{19.20}\)

=\(\frac{1}{1.2}-\frac{1}{19.20}\)

=\(\frac{189}{380}\)

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Nguyễn Thị Huyền
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NĐT_2004_asd
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Nguyễn Huy Tú
22 tháng 5 2017 lúc 21:26

Yêu cầu các CTV, các bạn làm sai giúp nhé! Nếu bạn muốn đáp án tham khảo thì sau đề vòng 1 mk sẽ giải nhé

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tôi biết câu cuối 

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NĐT_2004_asd
22 tháng 5 2017 lúc 21:23

bt câu cuối thì trả lời đi

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h123456
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Trần Ngọc Thiện
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Nguyễn Trà My
26 tháng 4 2015 lúc 16:11

\(A=\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+......+\frac{1}{2^{2014}}\)

\(\Rightarrow A

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Cửu vĩ linh hồ Kurama
6 tháng 9 2016 lúc 16:39

A < 1

xin lỗi mình không biết cách viết phân số!!!!

nha!!!!

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Nguyễn Vân Nhi
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Virgo Cá Tính
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Bui Thi Minh Thu
27 tháng 2 2017 lúc 14:42

Chào bạn !Mình kết bạn nha!

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Hoàng Minh Hoài
27 tháng 2 2017 lúc 14:44
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                               
\(B=\frac{3+1}{3}+\frac{8+1}{8}+...+\frac{2014.2016+1}{2014.2016}+\frac{2015.2017+1}{2015.2017}\)         
\(=\frac{2^2}{3}+\frac{3^2}{8}+....+\frac{2015^2}{2014.2016}+\frac{2016^2}{2015.2017}\)         
=\(\frac{2.2}{3}+\frac{3.3}{2.4}+...+\frac{2015.2015}{2014.2016}+\frac{2016.2016}{2015.2017}\)         
=\(\frac{\left(2.3....2015.2016\right)+\left(2.3.....2015.2016\right)}{\left(1.2.3.....2014.2015\right)+\left(3.4....2016.2017\right)}\)         
=\(2016+\frac{2}{2017}\)         
          
          
          
          
          
          
          
          
          
          
          
                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
 
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Virgo Cá Tính
4 tháng 3 2017 lúc 16:51

mấy chế ko giúp thì thôi lại còn nhấn linh tinh

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Tai Nguyen
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