\(\sqrt{0}=0\)

\(\sqrt{36}=6\)

\(\sqrt{225}=15\)

\(\sqrt{81}-\sqrt{49}=9-7=2\)

\(4\sqrt{81}+7\sqrt{64}=4⋅9+7⋅8=92\)

\(\sqrt{4}⋅\sqrt{25}=2⋅5=10\)

\((-6\sqrt{7})^2=(-6)^2⋅\sqrt{7}^2=36⋅7=252\text{.}\)

\((4\sqrt{7}+5)(4\sqrt{7}-5)=(4\sqrt{7})^2-5^2=16⋅7-25=112-25=87\text{.}\)

\((\sqrt{3})^2=3\text{.}\)

\(-4(\sqrt{8})^2=-4⋅8=-32\text{.}\)

\(6\sqrt{6}-5\sqrt{6}=\sqrt{6}\)

\(4\sqrt{2}⋅5\sqrt{23}=20\sqrt{46}\)

\({\sqrt{12} \over \sqrt{6}}=\sqrt{2}\)

\({8\sqrt{14} \over \sqrt{2}}=8⋅{\sqrt{14} \over \sqrt{2}}=8\sqrt{7}\)

\({21\sqrt{45} \over 3\sqrt{5}}={21 \over 3}⋅{\sqrt{45} \over \sqrt{5}}=7⋅\sqrt{9}=7⋅3=21\)