a) \(\sqrt{54}=\sqrt{9. 6}=\sqrt{3^2.6}=3\sqrt{6}.\)
b) \(\sqrt{108}=\sqrt{36.3}=\sqrt{6^2.3}=6\sqrt{3}.\)
c) \(0,1\sqrt{20000}=0,1\sqrt{10000.2}=0,1\sqrt{100^2.2}\)
\(=0,1.100\sqrt{2}=10\sqrt{2}\).
d) \(-0,05\sqrt{28800}=-0,05.\sqrt{144.100.2}\)
\(=-0,05\sqrt{12^2.10^2.2}\)
\(=-0,05.12.10\sqrt{2}=-6\sqrt{2}\).
e) \(\sqrt{7.63.a^{2}}=\sqrt{7.(3.21).a^2}=\sqrt{(7.3).21.a^2}\)
\(=\sqrt{21.21.a^2}=\sqrt{21^2.a^2}=21|a|\).