Question

Срочно
ЗАДАНИЕ НА ФОТО​

Answer 1

Объяснение:

12.

$\displaystyle\\0,5\sqrt{80}-\frac{1}{6} \sqrt{180} +9\sqrt{605} =0,5\sqrt{16*5}-\frac{1}{6} \sqrt{36*5} +9\sqrt{121*5} =\\\\=0,5*4*\sqrt{5} -\frac{6}{6} \sqrt{5} +9*11*\sqrt{5}=2\sqrt{5}-\sqrt{5} +99\sqrt{5}=100\sqrt{5}.$

13.

$\displaystyle\\\frac{a-1}{\sqrt{a+3} -2} =\frac{(a-1)*(\sqrt{a+3)}+2) }{(\sqrt{a+3} -2)*(\sqrt{a+3}+2) } =\frac{(a-1)*(\sqrt{a+3)}+2) }{(\sqrt{a+3})^2 -2^2} = \\\\\\=\frac{(a-1)*(\sqrt{a+3)}+2) }{a+3-4} =\frac{(a-1)*(\sqrt{a+3)}+2) }{a-1} =\sqrt{a+3} +2.$