[tex] \frac{4}{15}= \frac{2}{a}- \frac{2}{b} \Leftrightarrow \frac{2}{15}= \frac{1}{a}- \frac{1}{b} \Leftrightarrow \frac{2}{15}= \frac{b-a}{a \cdot b}. \\ \\ Putem~considera~(de~exemplu)~b=5~si~a=3. \\ \\ Astfel,~avem: \boxed{ \frac{4}{15}= \frac{2}{3}- \frac{2}{5} }~.[/tex]
