Question

[Nguyễn Văn Nhật Dũng]

tính hợp lý tổng sau

A= 1/1x2+1/2x3+1/3x4+.....+1/49x50

Answer 1

[Gà Game thủ]

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

A=\(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)

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

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