E necesar să cunoaștem primele pătrate perfecte,
cele mai uzuale : 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144
[tex]\it \sqrt8=\sqrt{4\cdot2}=2\sqrt2\\ \\ \sqrt{12}=\sqrt{4\cdot3}=2\sqrt3\\ \\ \sqrt{20}=\sqrt{4\cdot5}=2\sqrt5\\\rule{90}{\0.5}\\ \\ \sqrt{18}=\sqrt{9\cdot2}=3\sqrt2\\ \\ \sqrt{27}=\sqrt{9\cdot3}=3\sqrt3\\ \\ \sqrt{45}=\sqrt{9\cdot5}=3\sqrt5\\\rule{100}{0.6}\\ \\ \sqrt{50}=\sqrt{50\cdot2}=5\sqrt2\\ \\ \sqrt{75}=\sqrt{25\cdot3}=5\sqrt3\\ \\ \sqrt{125}=\sqrt{25\csot5}=5\sqrt5\\\rule{100}{0.6}\\ \\ \sqrt{32}=\sqrt{16\cdot2}=4\sqrt2\\ \\ \sqrt{48}=\sqrt{16\cdot3}=4\sqrt3\\ \\ \sqrt{80}=\sqrt{16\cdot5}=4\sqrt5[/tex]
