Question

Tính E

\(E=\dfrac{3^2}{8\times11}+\dfrac{3^2}{11\times14}+\dfrac{3^2}{14\times17}+...+\dfrac{3^2}{197\times200}\)

Answer 1

\(=3\left(\dfrac{3}{8\cdot11}+\dfrac{3}{11\cdot14}+...+\dfrac{3}{197\cdot200}\right)\)

\(=3\left(\dfrac{1}{8}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{14}+...+\dfrac{1}{197}-\dfrac{1}{200}\right)\)

\(=3\cdot\dfrac{192}{1600}=\dfrac{9}{25}\)