266. Упростите: a) ($$\sqrt{18}$$)^2; б) $$3\sqrt{7} \cdot \sqrt{7}$$; в) $$2\sqrt{10} \cdot \sqrt{10}\sqrt{2}$$; г) $$(2\sqrt{3})^2$$; д) $$(-2\sqrt{2})^2$$; e) $$(-3\sqrt{2})^2$$

а) ($$\sqrt{18}$$)^2 = 18

б) $$3\sqrt{7} \cdot \sqrt{7} = 3 \cdot 7 = 21$$

в) $$2\sqrt{10} \cdot \sqrt{10}\sqrt{2} = 2 \cdot 10 \cdot \sqrt{2} = 20\sqrt{2}$$

г) $$(2\sqrt{3})^2 = 4 \cdot 3 = 12$$

д) $$(-2\sqrt{2})^2 = 4 \cdot 2 = 8$$

e) $$(-3\sqrt{2})^2 = 9 \cdot 2 = 18$$