=>2B=2/1.3 +2/3.5 +2/5.7+...+2/2003.2005
=>2B=1-1/3+1/3-1/5+1/5-1/7+...+1/2003-1/2005
=>2B=-1/2005
=>B=-1/2005:2=-1/4010
Vậy B= -1/4010
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Các câu hỏi tương tự
a,tính \(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+......+\frac{1}{19.21}\)
b,CMR A\(=\frac{1}{1.3}+\frac{1}{3.5}+....+\frac{1}{(2n-1).(2n+1)}\le\frac{1}{2}\)
Thực hiện phép tính: \(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+....+\frac{1}{19.21}\)
Tính tổng: \(S=\frac{1}{1.3}-\frac{1}{2.4}+\frac{1}{3.5}-\frac{1}{4.6}+\frac{1}{5.7}-\frac{1}{6.8}+\frac{1}{7.9}-\frac{1}{8.10}\)
\(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+......+\frac{1}{19.21}\)
Tính
B=\(-\frac{1}{54}-\frac{3}{1.3}-\frac{3}{3.5}-\frac{3}{5.7}-...-\frac{3}{79.81}\)
\(\frac{1}{3}x.x=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{99.101}\)
TÌM x
Gía trị biểu thức:
\(\frac{1}{1.3}+\frac{1}{2.4}+\frac{1}{3.5}+\frac{1}{4.6}+\frac{1}{5.7}+\frac{1}{6.8}+\frac{1}{7.9}+\frac{1}{8.10}\)
Cho M=\(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{2017.2019}\)
So sanh M vs 1/2
Rút gọn Bt
A= \(\frac{1}{1.3}-\frac{1}{3.5}-\frac{1}{5.7}-.......-\frac{1}{47.49}-\frac{1}{49.51}\)