Question

Lamf hộ mình với

Answer 1

\(E=\frac{15}{11.14}+\frac{15}{14.17}+...+\frac{15}{74.77}\)

\(=5\left(\frac{3}{11.13}+\frac{3}{14.17}+...+\frac{3}{74.77}\right)\)

\(=5\left(\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+...+\frac{1}{74}-\frac{1}{77}\right)\)

\(=5\left(\frac{1}{11}-\frac{1}{77}\right)\)

\(=5.\frac{6}{77}\)

\(=\frac{30}{77}\)

Vậy \(E=\frac{30}{77}\)

Answer 2

30/77