What pair of factors should be used to find the complex solutions for​ x?

Question

What pair of factors should be used to find the complex solutions for​ x?

f(x)= x^4−4x^3+3x^2

Answer 1

None of the solutions are complex.

f(x) = x²(x - 3)(x - 1)

The zeros are 0 (twice), 3, and 1.

Answer 2

edited from similar answer

f(x)=(x-0)*(x-0)*(x-3)*(x-1) and no root includes square root -1

maybe it could be said that since x=0 is a repeated root

x=0+0*√-1 and x=0-0*√-1 are complex conjugate roots of

f(x)= x^4−4x^3+3x^2