3 x + 5*x
x^3 + 5*x
/ ___\ / ___\ x*\x + I*\/ 5 /*\x - I*\/ 5 /
(x*(x + i*sqrt(5)))*(x - i*sqrt(5))
/ 2\ x*\5 + x /
x*(5 + x^2)
x^3 + 5.0*x