\(\dfrac{a}{b}< 1\Leftrightarrow\dfrac{a}{b}< \dfrac{a+m}{b+m}\)\(\left(a,b,m\in N\cdot\right)\)
Ta có:
\(B=\dfrac{10^9+1}{10^{10}+1}< 10\left(10^9< 10^{10}\right)\)
\(\Leftrightarrow B=\dfrac{10^9+1}{10^{10}+1}< \dfrac{10^9+1+9}{10^{10}+1+9}=\dfrac{10^9+10}{10^{10}+10}=\dfrac{10\left(10^8+1\right)}{10\left(10^9+1\right)}=\dfrac{10^8+1}{10^9+1}=A\)
\(\Leftrightarrow A>B\)