Question

A=3/1.2 + 3/2.3 + 3/3.4 +................... 3/9.10

Giup mk nhé mà theo kiểu tiểu học nha !

Answer 1

A = \(\frac{3}{1.2}+\frac{3}{2.3}+\frac{3}{3.4}+...+\frac{3}{9.10}\)

A = \(\frac{3}{1}-\frac{3}{2}+\frac{3}{2}-\frac{3}{3}+\frac{3}{3}-\frac{3}{4}+...+\frac{3}{9}-\frac{3}{10}\)

A = \(\frac{3}{1}-\frac{3}{10}\)

A = \(\frac{27}{10}\)

Vậy A = \(\frac{27}{10}\)

Answer 2

\(\frac{3}{1\cdot2}+\frac{3}{2\cdot3}+\frac{3}{3\cdot4}+...+\frac{3}{9\cdot10}\)

\(=3\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-...-\frac{1}{10}\right)\)

\(=3\frac{9}{10}=\frac{27}{10}\)