Ta có :
\(C=\frac{3^2}{8.11}+\frac{3^2}{11.14}+\frac{3^2}{14.17}+...+\frac{3^2}{197.200}\)
\(C=3\left(\frac{3}{8.11}+\frac{3}{11.14}+\frac{3}{14.17}+...+\frac{3}{197.200}\right)\)
\(C=3\left(\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+...+\frac{1}{197}-\frac{1}{200}\right)\)
\(C=3\left(\frac{1}{8}-\frac{1}{200}\right)\)
\(C=3.\frac{3}{25}\)
\(C=\frac{9}{25}\)
Chúc bạn học tốt ~