B = \(\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{2015.2017}\)
B = \(\frac{1}{2}\left(\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{2015}-\frac{1}{2017}\right)\)
B = \(\frac{1}{2}\left(\frac{1}{1}-\frac{1}{2017}\right)\)
B = \(\frac{1}{2}\left(\frac{2017}{2017}-\frac{1}{2017}\right)\)
B = \(\frac{1}{2}.\frac{2016}{2017}\)
B = \(\frac{1008}{2017}\)
Vậy B = \(\frac{1008}{2017}\)
Chúc bạn học tốt . Có bài gì khó mik sẽ giúp bạn ( Chỉ toán 6 hoặc 7 trở xuống thui đó )
\(B=\frac{1}{1\cdot3}+\frac{1}{3\cdot5}+...+\frac{1}{2015\cdot2017}\)
\(B=\frac{1}{2}\left(\frac{2}{1\cdot3}+\frac{2}{3\cdot5}+...+\frac{2}{2015\cdot2017}\right)\)
\(B=\frac{1}{2}\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{2015}-\frac{1}{2017}\right)\)
\(B=\frac{1}{2}\left(1-\frac{1}{2017}\right)\)
\(B=\frac{1}{2}\cdot\frac{2016}{2017}\)
\(B=\frac{1008}{2017}\)
\(B=\frac{1}{1.3}+\frac{1}{3.7}+...+\frac{1}{2005.2007}\)
\(2B=\frac{2}{1.3}+\frac{2}{3.5}+....+\frac{2}{2015.2017}\)
\(2B=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+....+\frac{1}{2015}-\frac{1}{2017}\)
\(2B=1-\frac{1}{2017}\)
\(2B=\frac{2016}{2017}\)
\(B=\frac{2016}{2017}:2\)
\(B=\frac{1008}{2017}\)
Vậy \(B=\frac{1008}{2017}\)
