[tex]a=\frac{4}{\sqrt{6+2\sqrt{5}}}=\frac{4}{\sqrt{1+2\sqrt{5}+5}}= \frac{4}{\sqrt{(1+\sqrt{5} )^{2} }}}=\frac{4}{1+\sqrt{5}}\\ \\=\frac{4(1-\sqrt{5})}{(1+\sqrt{5} )(1-\sqrt{5})}=\frac{4(1-\sqrt{5})}{1-5}}=\frac{4(1-\sqrt{5})}{-4}}=-1+\sqrt{5}=\sqrt{5}-1[/tex]
Mg = √a×b = √(√5-1)(√5+1) = √(5 - 1) = √4 = 2
