[tex]Ai \ o \ formula \ de \ calcul \ prescurtat \ plus \ un \ radical \\
(a-b) ^{2} =a^2-2ab+b^2 \\ \\ (4- \sqrt{5})^2+8 \sqrt{5}= \\ =4^2-2*4* \sqrt{5}+ (\sqrt{5})^2+8 \sqrt{5} \\ =16-8 \sqrt{5}+5+8 \sqrt{5} \ radicalii \ se \ simplifica \\ =16+5= \\ =\boxed{21} [/tex]
