$\textit{laviken}$
Giải thích các bước giải:
a)
$\text{A=}$ ($\dfrac{1}{2}$-1).($\dfrac{1}{3}$-1)....($\dfrac{1}{10}$-1)
$\text{A=}$ ($\dfrac{1}{2}$-$\dfrac{2}{2}$).($\dfrac{1}{3}$-$\dfrac{3}{3}$)....($\dfrac{1}{10}$-$\dfrac{10}{10}$)
$\text{A=}$ ($\dfrac{-1}{2}$).($\dfrac{-2}{3}$)....($\dfrac{-9}{10}$)
$\text{A=}$ $\dfrac{-1}{2}$.$\dfrac{-2}{3}$....$\dfrac{-9}{10}$
$\text{A=}$ $\dfrac{(-1).(-2).....(-9)}{2.3....10}$ = $\dfrac{-1}{10}$
$\textit${Mà}$\dfrac{-1}{10}$ > $\dfrac{-1}{9}$ $\textit${nên} A > $\dfrac{-1}{9}$
b) $\underline{Tương tự nhé =.=}$
