a, A = \(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{99}-\dfrac{1}{101}=1-\dfrac{1}{101}=\dfrac{100}{101}\)
b, B = \(5\left(1-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{11}+...+\dfrac{1}{21}-\dfrac{1}{26}\right)=\dfrac{5.25}{26}=\dfrac{125}{26}\)
c, \(C=\dfrac{3}{2}\left(1-\dfrac{1}{3}+\dfrac{1}{3}+...+\dfrac{1}{49}-\dfrac{1}{51}\right)=\dfrac{3}{2}.\dfrac{50}{51}=\dfrac{25}{17}\)
e, \(E=\dfrac{1}{4}\left(\dfrac{1}{3}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{15}+...+\dfrac{1}{107}-\dfrac{1}{111}\right)=\dfrac{3}{37}\)
bổ sung d
D = \(\dfrac{1}{1.7}+\dfrac{1}{7.13}+\dfrac{1}{13.19}+\dfrac{1}{19.25}+\dfrac{1}{25.31}+\dfrac{1}{31.37}\)
\(=1-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{13}+\dfrac{1}{13}+...+\dfrac{1}{31}-\dfrac{1}{37}=\dfrac{36}{37}\)
