Question

Tinh A

 A= 1/30 + 1/42 + 1/56 + 1/72 + ... + 1/132

Answer 1

A = 1/30 + 1/42 + 1/56 + 1/72 + ... + 1/132

A = 1/5.6 + 1/6.7 + 1/7.8 + 1/8.9 + ... + 1/11.12

A = 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8 + 1/8 - 1/9 + ... + 1/11 - 1/12

A = 1/5 - 1/12

A = 7/30

Answer 2

\(A=\frac{1}{5.6}+\frac{1}{6.7}+...+\frac{1}{11.12}\)

\(=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+...+\frac{1}{11}-\frac{1}{12}\)

\(=\frac{1}{5}-\frac{1}{12}\)

\(=\frac{7}{60}\)

Answer 3

A = 1/30 + 1/42 + 1/56 + 1/72 + ... + 1/132

A = 1/5.6 + 1/6.7 + 1/7.8 + 1/8.9 + ... + 1/11.12

A = 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8 + 1/8 - 1/9 + ... + 1/11 - 1/12

A = 1/5 - 1/12

A = 7/30