Question

Tính 

A = 1/1.2 + 1/2.3 + ... + 1/49.50 

Answer 1

\(A=1.\left[\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+.....+\frac{1}{49}-\frac{1}{50}\right]\)

\(A=1.\left[1-\frac{1}{50}\right]\)

\(A=\frac{49}{50}\)

mk làm đầu tiên đó

Answer 2

A=\(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{49.50}\)

A=\(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{49}-\frac{1}{50}\)

A=\(1-\frac{1}{50}\)

A=\(\frac{50}{50}-\frac{1}{50}\)

A=\(\frac{49}{50}\)

       Vậy A=\(\frac{49}{50}\)