\(TH1:a< b\Rightarrow\dfrac{a}{b}< 1=\dfrac{n}{n}\)
\(\dfrac{a}{b}< \dfrac{a+n}{b+n}\)
\(TH2:a>b\Rightarrow\dfrac{a}{b}>1=\dfrac{n}{n}\)
\(\dfrac{a}{b}>\dfrac{a+n}{b+n}\)
\(TH3:a=b\Rightarrow\dfrac{a}{b}=1=\dfrac{n}{n}\)
\(\dfrac{a}{b}=\dfrac{a+n}{b+n}\)