Question

Даю 25 баллов!!!!!!!!!!!!

Answer 1

Ответ:

$1)\sqrt{a}+2;\\2) 1-\sqrt{23} ;\\3)\frac{\sqrt{a}+\sqrt{5}}{\sqrt{a}-\sqrt{5}}$

Объяснение:

$\displaystyle1)\frac{a-4}{\sqrt{a}-2} =\frac{(\sqrt{a}-2)(\sqrt{a}+2)}{\sqrt{a}-2} =\sqrt{a}+2;\\2)\frac{\sqrt{23} -23}{\sqrt{23} } =\frac{\sqrt{23} (1-\sqrt{23} )}{\sqrt{23} } =1-\sqrt{23} ;\\3)\frac{a-5}{a+2\sqrt{5a}+5 } =\frac{a-5}{(\sqrt{a}-\sqrt{5} )^{2} } =\frac{(\sqrt{a}-\sqrt{5} )(\sqrt{a}+\sqrt{5} ) }{(\sqrt{a}-\sqrt{5} )^{2} } =\frac{\sqrt{a}+\sqrt{5}}{\sqrt{a}-\sqrt{5}}\\---------------\\\bf (a\pm b)^{2} =a^{2}\pm2ab+b^{2};\\a^{2}-b^{2}=(a-b)(a+b);\\\sqrt{x^{2} } = |x|$