A=1-1/3+1/3-1/5+1/5-1/7+...+1/99-1/100
A=1-1/100
A=99/100
\(A=\frac{2}{1\cdot3}+\frac{2}{3\cdot5}+...+\frac{2}{99\cdot101}=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{101}\)\(=\left(1-\frac{1}{101}\right)+\left(\frac{1}{3}-\frac{1}{3}\right)+\left(\frac{1}{5}-\frac{1}{5}\right)+...+\left(\frac{1}{99}-\frac{1}{99}\right)=\left(\frac{101}{101}-\frac{1}{101}\right)+0+0+...+0=\frac{100}{101}\)Chúc bạn học tốt!^_^