Răspuns:
[tex]\displaystyle 3\sqrt{5} \ = \sqrt{3^2\cdot5} = \ \sqrt{9\ \cdot \ 5} = \sqrt{45} \\\\ \displaystyle 2^{3}\sqrt{2} \ = \ \sqrt{2^6\cdot2} \ = \ \sqrt{64 \ \cdot \ 2} \ = \ \sqrt{128} \\\\ \displaystyle - \ 2 \sqrt{5} \ = \ -\sqrt{2^2\cdot5} = \ - \ \sqrt{4 \ \cdot \ 5} \ = \ - \sqrt{20} \\\\[/tex]
