Question

[công chúa chipu]

\(\frac{5}{10.11}+\frac{5}{11.12}+\frac{5}{12.13}+\frac{5}{13.14}+\frac{5}{14.15}\)

Answer 1

[dinhkhachoang]

5/10.11+5/11.12+5/12.13+5/13.14+5/14.15

=1/10-1/11+1/11-1/12+.....+1/14-1/15

=1/10-1/15

=1/30

Answer 2

[Trần Quang Đài]

\(=5\left(\frac{1}{10.11}+\frac{1}{11.12}+...+\frac{1}{14.15}\right)\)

\(5\left(\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-...+\frac{1}{14}-\frac{1}{15}\right)\)

\(5\left(\frac{1}{10}-\frac{1}{15}\right)\)

\(=\frac{1}{2}-\frac{1}{3}=\frac{1}{6}\)