Question

Tính giá trị biểu thức:

\(\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+...+\frac{1}{21.22}\)

(TRÌNH BÀY CÁCH TÍNH RÕ RÀNG)

 

Answer 1

Đặt \(A=\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+...+\frac{1}{21.22}\)

\(A=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+...+\frac{1}{21}-\frac{1}{22}\)

\(A=\frac{1}{5}-\frac{1}{22}\)

\(A=\frac{17}{110}\)

Answer 2

\(\frac{1}{5.6}\)+\(\frac{1}{6.7}\)+...+\(\frac{1}{21.22}\)

=\(\frac{1}{5}\)-\(\frac{1}{6}\)+\(\frac{1}{6}\)-\(\frac{1}{7}\)+...+\(\frac{1}{21}\)-\(\frac{1}{22}\)

=\(\frac{1}{5}\)-\(\frac{1}{22}\)

=\(\frac{17}{110}\)

Answer 3

\(A=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+...+\frac{1}{21}-\frac{1}{22}\)

\(A=\frac{1}{5}-\frac{1}{22}\)

\(A=\frac{22}{110}-\frac{5}{110}\)

\(A=\frac{17}{110}\)