Question

помогите пожалуйста решить все​

Answer 1

$\displaystyle\tt 1) \ 3\sqrt{20} +\sqrt{28}+\sqrt{45}-\sqrt{63}=3\cdot2\sqrt{5}+2\sqrt{7}+3\sqrt{5}-3\sqrt{7}= \\\\ {}\ \ \ =9\sqrt{5}-\sqrt{7}$

$\displaystyle\tt 2) \ \left(2\sqrt{\frac{2}{3}}-8\sqrt{\frac{3}{8}}+3\sqrt{\frac{3}{2}}\right)\cdot 3\sqrt{\frac{3}{2}}=\\\\\\{} \ \ \ =2\sqrt{\frac{2}{3}}\cdot 3\sqrt{\frac{3}{2}}-8\sqrt{\frac{3}{8}}\cdot 3\sqrt{\frac{3}{2}}+3\sqrt{\frac{3}{2}}\cdot 3\sqrt{\frac{3}{2}}=\\\\\\{} \ \ \ =6-24\sqrt{\frac{9}{16}}+9\sqrt{\frac{9}{4}}=6-24\cdot\frac{3}{4}+9\cdot\frac{3}{2} =6-18+13,5=1,5$

$\displaystyle\tt 3) \ (6\sqrt{45}-3\sqrt{20}+9\sqrt{80}):(3\sqrt{5})=(18\sqrt{5}-6\sqrt{5}+36\sqrt{5}):(3\sqrt{5})=\\\\{} \ \ \ =(48\sqrt{5}):(3\sqrt{5})=16$

$\displaystyle\tt 4) \ (7\sqrt{8}-14\sqrt{18}+0,7\sqrt{12}):(7\sqrt{2})=\\\\{} \ \ \ =(14\sqrt{2}-42\sqrt{2}+1,4\sqrt{3}):(7\sqrt{2})=(-28\sqrt{2}+1,4\sqrt{3}):(7\sqrt{2})=\\\\{} \ \ \ =(-28\sqrt{2}):(7\sqrt{2})+(1,4\sqrt{3}):(7\sqrt{2})=-4+0,2\sqrt{\frac{3}{2} }$