Упростите выражения.

Решите задачу:

$2) ( \sqrt{6} + \sqrt{3})\sqrt{12}- 2\sqrt{6} * \sqrt{3} = \sqrt{6*12} + \sqrt{3*12}-2 \sqrt{6*3}=\\= \sqrt{72} + \sqrt{36} -2\sqrt{18}= \sqrt{36*2}+6-2 \sqrt{9*2} = 6\sqrt{2} +6- 6\sqrt{2}=\\=6\\\\\\3) (\frac{6}{y^2-9} + \frac{1}{3-y})* \frac{y^2+6y+4}{5}=( \frac{6}{(y-3)(y+3)} - \frac{1}{y-3})* \frac{(y+3)^2}{5}=\\\\=( \frac{6 -y-3}{(y-3)(y+3)})* \frac{(y+3)^2}{5} = \frac{(3-y)(y+3)^2}{5(y-3)(y+3)} = - \frac{(y-3)(y+3)}{5(y-3)}= \frac{y+3}{5}$