Question

a,A=\(\frac{1}{10\times11}+\frac{1}{11\times12}+...+\frac{1}{99\times100}\)

Answer 1

\(A=\frac{1}{10\times11}+\frac{1}{11\times12}+...+\frac{1}{99\times100}\)

\(A=\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+...+\frac{1}{99}-\frac{1}{100}\)

\(A=\frac{1}{10}-\frac{1}{100}\)

\(A=\frac{9}{100}\)

Answer 2

\(A=\frac{1}{10.11}+\frac{1}{11.12}+...+\frac{1}{99.100}\)

\(=\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+...+\frac{1}{99}-\frac{1}{100}\)

\(=\frac{1}{10}-\frac{1}{100}\)

\(=\frac{9}{100}\)

Answer 3

9/100 nha bn

chuc bn hoc tot

happy new year