Odpowiedź:
[tex]a)\ \ \sqrt{5}(3-\sqrt{5})=3\sqrt{5}-\sqrt{5}\cdot\sqrt{5}=3\sqrt{5}-\sqrt{25}=3\sqrt{5}-5\\\\b)\ \ \sqrt{2}(5\sqrt{2}-3)=\sqrt{2}\cdot5\sqrt{2}-3\sqrt{2}=\sqrt{4}\cdot5-3\sqrt{2}=2\cdot5-3\sqrt{2}=10-3\sqrt{2}\\\\c)\ \ -\sqrt{3}(2\sqrt{3}+5)=-\sqrt{3}\cdot2\sqrt{3}-5\sqrt{3}=-\sqrt{9}\cdot2-5\sqrt{3}=-3\cdot2-5\sqrt{3}=-6-5\sqrt{3}\\\\d)\ \ 2\sqrt{7}(4+\sqrt{7})=2\sqrt{7}\cdot4+2\sqrt{7}\cdot\sqrt{7}=8\sqrt{7}+2\cdot\sqrt{49}=8\sqrt{7}+2\cdot7=8\sqrt{7}+14[/tex]
