а) ($$\sqrt{18}$$)2 = 18
б) 3$${\sqrt{7}}$$ · $${\sqrt{7}}$$ = 3 * 7 = 21
в) 2$${\sqrt{10}}$$ · $${\sqrt{10}}$$ · $${\sqrt{2}}$$ = 2 * 10 * $${\sqrt{2}}$$ = 20$${\sqrt{2}}$$
г) (2$${\sqrt{3}}$$)2 = 4 * 3 = 12
д) (-$${\sqrt{2}}$$)2 = 2
е) (-3$${\sqrt{2}}$$)2 = 9 * 2 = 18