tớ ko chép lại đề đâu
\(\frac{1}{2}M=\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+...+\frac{2}{101.103}\)
\(=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{101}-\frac{1}{103}\)
\(=\frac{1}{5}-\frac{1}{103}\)
=\(\frac{98}{515}\)
=> \(M=\frac{98}{515}:\frac{1}{2}=\frac{196}{515}\)
Vậy \(M=\frac{196}{515}\)
\(M=\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}+.....+\frac{1}{101.103}\)
\(2M=\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+....+\frac{2}{101.103}\)
\(2M=\frac{7-5}{5.7}+\frac{9-7}{7.9}+\frac{11-9}{9.11}+.....+\frac{103-101}{101.103}\)
\(2M=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+.....+\frac{1}{101}-\frac{1}{103}\)
\(2M=\frac{1}{5}-\frac{1}{103}\)
\(2M=\frac{88}{515}\)
\(M=\frac{88}{515}.\frac{1}{2}\)
\(M=\frac{44}{515}\)
Vậy \(M=\frac{44}{515}\)
M=2(1/5.7+1/7.9+1/9.11+....+1/101.103)
M=1(2/5.7+2/7.9+1/9.11+....+1/101.103)
M=2/5-2/7+2/7-2/9+2/9-2/11+....+1/101-1/103
M=2/5-1/103
M=206/515-5/515
M=201/515
