Question

Помогите срочно! дам 35 баллов!

Answer 1

    $\boxed{\ (a-b)(a+b)=a^2-b^2\ }$

$(\sqrt{5}-\sqrt{11})(\sqrt{6}+\sqrt{11})=(\sqrt{5})^2-(\sqrt{11})^2=5-11=-6\\\\\\(3-\sqrt{5})(3+\sqrt{5})=3^2-(\sqrt{5})^2=9-5=4\\\\\\(2\sqrt5-1)(2\sqrt5+1)=(2\sqrt5)^2-1^2=4\cdot 5-1=20-1=19$

Answer 2

$1)(\sqrt{5} -\sqrt{11})(\sqrt{5}+\sqrt{11})=(\sqrt{5} )^{2}-(\sqrt{11} )^{2}=5-11=\boxed{-6}\\\\2)(3-\sqrt{5})(3+\sqrt{5})=3^{2} -(\sqrt{5})^{2}=9-5=\boxed4\\\\3)(2\sqrt{5}-1)(2\sqrt{5}+1)=(2\sqrt{5})^{2}-1^{2}=4*5-1=20-1=\boxed{19}$