a=5√5-6√5=-√5
b=3√5+4√5=7√5
ma=(a+b)/2=(-√5+7√5)/2=3√5
Am descompus radicalii pt a avea termeni asemenea.
[tex] \displaystyle\\
a= \sqrt{125}-3\sqrt{20}= \sqrt{25\times 5}-3\sqrt{4\times 5}=\\
=5\sqrt{5} -3\times 2\sqrt{5}= 5\sqrt{5} -6\sqrt{5}=\boxed{\bf -\sqrt{5}}\\\\
b = 3\sqrt{5} + \sqrt{80}= 3\sqrt{5}+ \sqrt{16\times 5}=3\sqrt{5}+ 4\sqrt{5}=\boxed{\bf 7\sqrt{5}}\\\\
m_a = \frac{a+b}{2}=\frac{-\sqrt{5}+7\sqrt{5}}{2}=\frac{6\sqrt{5}}{2}=\boxed{\bf 3\sqrt{5}}
[/tex]
