Aratati ca daca a>0, n apartine multimii numerelor naturale, n≥2 x=[tex] \sqrt[n]{a ^{p-q} } [/tex] y=[tex] \sqrt[n]{a^{p-q} } \sqrt{a^{r-q} } [/tex] si z=[tex] \sqrt{a ^{p-q} } \sqrt{a^{r-q} } \sqrt{a^{r-p}[/tex] . Demonstrati ca x, y si z sunt in progresie geometrica