Tính giá trị của A = 2/(1.4) + 2/(4.7)+... +2/(97.100)

A = 2/(1.4) + 2/(4.7) + 2/(7.10) + ... + 2/(97.100)

A = 2/3 . (1 - 1/4 + 1/4 - 1/7 + 1/7 +...- 1/97 + 1/97 - 1/100)

A = 2/3 . (1 - 1/100)

A = 2/3. 99/100 = 33/50

\(A=\frac{2}{1.4}+\frac{2}{4.7}+...+\frac{2}{97.100}\)

\(=\frac{2}{3}.\left(\frac{3}{1.4}+\frac{3}{4.7}+...+\frac{3}{97.100}\right)\)

\(=\frac{2}{3}.\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}...-\frac{1}{97}+\frac{1}{97}-\frac{1}{100}\right)\)

\(=\frac{2}{3}.\left(1-\frac{1}{100}\right)\)

\(=\frac{2}{3}.\frac{99}{100}=\frac{33}{50}\)

A = 33/50