Bài 3:
\(A=\dfrac{10^9+1}{10^{10}+1}\Rightarrow10A=\dfrac{10^{10}+10}{10^{10}+1}\Rightarrow10A-1=\dfrac{9}{10^{10}+1}\)
\(B=\dfrac{10^8+1}{10^9+1}\Rightarrow10B=\dfrac{10^9+10}{10^9+1}\Rightarrow10B-1=\dfrac{9}{10^9+1}\)
\(Do\) \(\dfrac{9}{10^{10}+1}< \dfrac{9}{10^9+1}\Rightarrow10A-1< 10B-1\Rightarrow10A< 10B\Rightarrow A< B\)