Question

[Nguyễn Hà Vy]

tính tống sau bằng cách hợp lý:

A= \(\dfrac{1}{2x3}\)\(+\)\(\dfrac{1}{3x4}+\dfrac{1}{4x5}+\dfrac{1}{5x6}+\dfrac{1}{6x7}\)

Answer 1

[Hoàng Bảo Minh]

A=\(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
A=\(\frac{1}{2}-\frac{1}{7}\)
A=\(\frac{5}{14}\)

Answer 2

[Nguyễn Thế Hùng]

A = 1/2 -1/3 +1/3-1/4 + 1/4-1/5 +1/5-1/6 + 1/6-1/7 =

1/2-1/7 = 5/14