Question

tính bằng cách nhanh nhất : A=\(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{49.50}\)

Answer 1

Ta có: \(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+.....+\frac{1}{49.50}\)

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

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

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

Answer 2

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

Answer 3

Đặt A = 1/1.2 + 1/2.3 + 1/3.4 + .... + 1/49.50

A = 1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/49 - 1/50

A = 1/1 - 1/50

A = 49/50

 Vậy A = 49/50

Answer 4

A = 1 - 1/2 + 1/2 - 1/3 + 1/3 +..... + 1/49 - 1/50

A = 1 - 1/50

A = 49/50

K mk nha. Ths 

Answer 5

\(\frac{49}{50}\)nhé