Question

tinh gai tri bieu thuc :

E=\(\frac{15}{11\cdot14}+\frac{15}{14\cdot17}+\frac{15}{17+20}+...+\frac{15}{74\cdot77}\)

Answer 1

ra 30/77 bạn ơi

Answer 2

\(E=\frac{15}{11.14}+\frac{15}{14.17}+\frac{15}{17.20}+.....+\frac{15}{74.77}\)

\(=\frac{15}{3}\left(\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+....+\frac{1}{74}-\frac{1}{77}\right)\)

\(=\frac{15}{3}\left(\frac{1}{11}-\frac{1}{77}\right)\)

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

Answer 3

\(E=\frac{15}{11.14}+\frac{15}{14.17}+\frac{15}{17.20}+......+\frac{15}{74.77}\)

\(\frac{15}{3}E\left(\frac{1}{11.14}+\frac{1}{14.17}+\frac{1}{17.20}+...+\frac{1}{74.77}\right)\)

\(\frac{15}{3}E=\left(\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+...+\frac{1}{74}-\frac{1}{77}\right)=>\frac{15}{3}E\left(\frac{1}{77}-1\right)\)

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

Answer 4

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

\(E=\frac{15}{3}\left(\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+...+\frac{1}{74}-\frac{1}{77}\right)\)

\(E=\frac{15}{3}\left(\frac{1}{11}-\frac{1}{77}\right)\)

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

Answer 5

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

\(E=\frac{15}{3}\left(\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+...+\frac{1}{74}-\frac{1}{77}\right)\)

\(E=\frac{15}{3}\left(\frac{1}{11}-\frac{1}{77}\right)\)

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

Answer 6

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

\(E=\frac{15}{3}\left(\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+...+\frac{1}{74}-\frac{1}{77}\right)\)

\(E=\frac{15}{3}\left(\frac{1}{11}-\frac{1}{77}\right)\)

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

Answer 7

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

\(E=\frac{15}{3}\left(\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}+...+\frac{1}{74}-\frac{1}{77}\right)\)

\(E=\frac{15}{3}\left(\frac{1}{11}-\frac{1}{77}\right)\)

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