help me !

F(x)=x^3+3x^2+4x+12

Factor to  find the roots

x^2(x + 3) + 4(x + 3)  = 0

(x^2 + 4) (x + 3)  = 0

Set the factors to 0

x^2 + 4  =0                    x +  3  = 0

x^2  = − 4                      x    =  − 3

x = ± i√ 4

x = ± 2i

So.....the roots are ± 2i  and − 3

which of the following is a root of the polynomial function? F(x)=x^3+3x^2+4x+12

Your question is not complete but it doesn't matter.

IF the number a is a root then  f(a)=0