Official solution
x2 + (20)1/4x + (5)1/2 = 0
\[ \Rightarrow \] x2 + \[\sqrt 5\] = - (20)1/4x
Squaring both sides, we get
\[{\left( {{x^2} + \sqrt 5 } \right)^2} = \sqrt {20} {x^2}\]
\[ \Rightarrow \] x4 = -5 \[\Rightarrow\] x8 = 25
\[ \Rightarrow \] \[\alpha\]8 + \[\beta\]8 = 50