How do I factor x^2+4x+20

Its like x² + 4x +20 = 0,
x = [-4 + √[(4²) - (4*1*20)]]/(2*1) = [-4 + √(16-80)]/2 = [-4 + √(-64)]/2 = [-4 + 8√(-1)]/2 = -2 + 4i,
x = [-4 - √[(4²) - (4*1*20)]]/(2*1) = [-4 - √(16-80)]/2 = [-4 - √(-64)]/2 = [-4 - 8√(-1)]/2 = -2 - 4i,
here i = √(-1), its a complex number.
so solution is a complex number,
x = -2 - 4i & -2 + 4i.