Question

Giá trị của biểu thức A = \(\dfrac{1}{\text{1 x 2}}\) + \(\dfrac{1}{\text{2 x 3}}\) + \(\dfrac{1}{\text{3 x 4}}\) là

Answer 1

A = 1/1 - 1/2 + 1/3 - 1/3 + 1/4

A = 1/1 - 1/4

A = 3/4

vậy A = 3/4

Answer 2

\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}\)

\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}\)

\(=1-\dfrac{1}{4}=\dfrac{4-1}{4}=\dfrac{3}{4}\)

Answer 3

\(A=\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}\)
\(=1-\dfrac{1}{4}\)
\(=\dfrac{3}{4}\)

#Sahara

Answer 4

a= 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4

a= 1 - 1/4

a= 3/4