Question

Tính

A=5/11.16+5/16.21+5/21.26+...+5/61.66

chúc các bạn học tốt

Answer 1

\(A=\frac{5}{11.16}+\frac{5}{16.21}+...+\frac{5}{61.66}\)

\(=\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+...+\frac{1}{61}-\frac{1}{66}\)

\(=\frac{1}{11}-\frac{1}{66}=\frac{5}{66}\)

Answer 2

\(A=\frac{5}{11.16}+\frac{5}{16.21}+\frac{5}{21.26}+...+\frac{5}{61.66}\)

\(A=\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+\frac{1}{21}-\frac{1}{26}+...+\frac{1}{61}-\frac{1}{66}\)

\(A=\frac{1}{11}-\frac{1}{66}\)

\(A=\frac{6}{66}-\frac{1}{66}\)

\(A=\frac{5}{66}\)

Answer 3

=\(\frac{5}{11}\).\(\frac{5}{16}\)+\(\frac{5}{16}.\frac{5}{21}+\frac{5}{21}.\frac{5}{26}+...\frac{5}{61}.\frac{5}{66}\)

=\(\frac{5}{11}.\frac{5}{66}\)

=\(\frac{25}{726}\)

Answer 4

Ta có :A= \(\frac{5}{11\cdot16}+\frac{5}{16\cdot21}+\frac{5}{21\cdot26}+...+\frac{5}{61\cdot66}\)

=\(\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+\frac{1}{21}-\frac{1}{26}+...+\frac{1}{61}-\frac{1}{66}\)

=\(\frac{1}{11}-\frac{1}{66}\)

=\(\frac{5}{66}\)

Chúc bạn học tốt !

Answer 5

\(\frac{5}{11.16}+\frac{5}{16.21}+\frac{5}{21.26}+....+\frac{5}{61.66}\)

\(=5\left(\frac{1}{11.16}+\frac{1}{16.21}+\frac{1}{21.26}+....+\frac{1}{61.66}\right)\)

\(=5(\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+\frac{1}{21}-\frac{1}{26}+....+\frac{1}{61}-\frac{1}{66})\)

\(=5\left(\frac{1}{11}-\frac{1}{66}\right)\)

\(=5\left(\frac{6}{66}-\frac{1}{66}\right)\)

\(5.\frac{5}{66}=\frac{25}{66}\)