Question 973435
(x-1)(x-4)(X^2+4)=0.  The last must have two roots, +/- 2i

(x^2-5x+4)(x^2 +4)=0
x^4-5x^3+8x^2-20x+16

{{{graph(300,300,-5,10,-30,70,x^4-5x^3+8x^2-20x+16)}}}