Question

Помогите упростить! 1) √2а-2√18а+√72а; 2) √5а-3√20а+√125а.

Answer 1

$1) \sqrt{2a}-2 \sqrt{18a} + \sqrt{72a}=\sqrt{2a}-2\sqrt{9*2a}+\sqrt{36*2a}= \\ =\sqrt{2a}-2*3\sqrt{2a}+6\sqrt{2a}=\sqrt{2a}-6\sqrt{2a}+6\sqrt{2a}=\sqrt{2a} \\ \\ 2) \sqrt{5a} -3\sqrt{20a}+\sqrt{125a}=\sqrt{5a}-3\sqrt{4*5a}+\sqrt{25*5a}= \\ =\sqrt{5a}-3*2\sqrt{5a}+5\sqrt{5a}=\sqrt{5a}-6\sqrt{5a}+5\sqrt{5a}=0$