Bonsoir
[tex]a=2\sqrt{45}=2\sqrt{9\times 5}=2\sqrt{9}\times \sqrt{5}= 2\times3\times\sqrt{5}\\\\a=6\sqrt{5}[/tex]
[tex]b=\sqrt{80}=\sqrt{16\times5}=\sqrt{16}\times\sqrt{5}\\\\b=4\sqrt{5}[/tex]
[tex]1)\ a)\ a+b=6\sqrt{5}+4\sqrt{5}\\\\a+b=10\sqrt{5}\\\\\\\\b)\ ab = (6\sqrt{5})\times(4\sqrt{5})\\\\ab = 6\times4\times\sqrt{5}\times\sqrt{5}\\\\ab = 6\times4\times(\sqrt{5})^2\\\\ab = 6\times4\times5\\\\ab=120[/tex]
