Question

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

Answer 1

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

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

A=\(1-\frac{1}{4}\)

A=\(\frac{3}{4}\)

Answer 2

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

\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}=\frac{6}{12}+\frac{2}{12}+\frac{1}{12}=\frac{9}{12}=\frac{3}{4}\)