Question

5^2/1.6 + 5²2/6.11 + 5²2/11.16+ ... + 5²2/46.51

 

 

Answer 1

Ta có : 

\(\frac{5^2}{1.6}+\frac{5^2}{6.11}+\frac{5^2}{11.16}+...+\frac{5^2}{46.51}\)

\(=\)\(5\left(\frac{5}{1.6}+\frac{5}{6.11}+\frac{5}{11.16}+...+\frac{5}{46.51}\right)\)

\(=\)\(5\left(\frac{1}{1}-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+\frac{1}{11}-\frac{1}{16}+...+\frac{1}{46}-\frac{1}{51}\right)\)

\(=\)\(5\left(1-\frac{1}{51}\right)\)

\(=\)\(5.\frac{50}{51}\)

\(=\)\(\frac{250}{51}\)

Chúc bạn học tốt ~