Question

Cho 

A=\(\left(\frac{1}{2}-1\right)\left(\frac{1}{3}-1\right)\left(\frac{1}{4}-1\right).....\left(\frac{1}{10}-1\right)\)

So sánh A với \(\frac{-1}{9}\)

Answer 1

\(A=\left(\frac{1}{2}-1\right)\left(\frac{1}{3}-1\right)\left(\frac{1}{4}-1\right)...\left(\frac{1}{10}-1\right)\)

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

\(\Rightarrow A=\frac{-1}{10}\)

Dễ thấy \(\frac{1}{10}< \frac{1}{9}\Rightarrow\frac{-1}{10}>\frac{-1}{9}\)

Answer 2

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

\(A=\frac{-1}{10}\)

\(\frac{-1}{10}>\frac{-1}{9}\Rightarrow A>\frac{-1}{9}\)

đ/s:..

Answer 3

kk k mik mik mik nha nha nha!