800 Вправа 800Алгебра 8 клас Бевз 2025 · § 16 · стор. 153

800. Виконай дії.

а) ${\displaystyle (\sqrt{20}+\sqrt{45})\cdot \sqrt{5}=}$${\displaystyle \sqrt{100}+\sqrt{225}}$=

=${\displaystyle 10+15=}$${\displaystyle 25}$;

б) ${\displaystyle (\sqrt{63}-\sqrt{28})\cdot \sqrt{7}=}$${\displaystyle \sqrt{441}-\sqrt{196}}$=

=${\displaystyle 21-14=}$${\displaystyle 7}$;

в) ${\displaystyle (7\sqrt{24}-5\sqrt{54})\cdot \sqrt{6}=}$${\displaystyle (14\sqrt{6}-15\sqrt{6})\cdot \sqrt{6}}$=

=${\displaystyle -\sqrt{6}\cdot \sqrt{6}=}$${\displaystyle -6}$;

г) ${\displaystyle (5\sqrt{12}-3\sqrt{3})\cdot 2\sqrt{3}=}$${\displaystyle (10\sqrt{3}-3\sqrt{3})\cdot 2\sqrt{3}}$=

=${\displaystyle 7\sqrt{3}\cdot 2\sqrt{3}=}$${\displaystyle 14\cdot 3=}$${\displaystyle 42}$.