a.
\(10A=\dfrac{10^{11}+10}{10^{11}+1}=\dfrac{10^{11}+1+9}{10^{11}+1}=1+\dfrac{9}{10^{11}+1}\)
\(10B=\dfrac{10^{10}+10}{10^{10}+1}=\dfrac{10^{10}+1+9}{10^{10}+1}=1+\dfrac{9}{10^{10}+1}\)
Mà \(\dfrac{1}{10^{10}+1}>\dfrac{1}{10^{11}+1}\)
\(\Rightarrow10B>10A\Rightarrow B>A\)
b.
Làm hoàn toàn tương tự câu a, so sánh 5M và 5N