a) \(\frac{a}{b}>1\Rightarrow\frac{a}{b}.b>1.b\Rightarrow a>b\)
\(a>b\Rightarrow\frac{a}{b}>\frac{b}{b}\Rightarrow\frac{a}{b}>1\)
b) \(\frac{a}{b}< 1\Rightarrow\frac{a}{b}.b< 1.b\Rightarrow a< b\)
\(a< b\Rightarrow\frac{a}{b}< \frac{b}{b}\Rightarrow\frac{a}{b}< 1\)