\(\frac{5}{1.3}+\frac{5}{3.5}+\frac{5}{5.7}+...+\frac{5}{101.103}\)
\(=\frac{2}{5}.\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5,7}+...+\frac{2}{101.103}\right)\)
\(=\frac{2}{5}.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{101}-\frac{1}{103}\right)\)
\(=\frac{2}{5}\left(1-\frac{1}{103}\right)\)
\(=\frac{2}{5}.\left(\frac{102}{103}\right)=\frac{204}{515}\)
Nhớ kiểm tra lại cho kl nhé
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