Question

solve each equation
3x^3+12x^2-x-4=0

Answer 1

I made a mistake putting it up! just edited. can you look again please

Answer 2

3x^3+12x^2-x-4=0
3x^2(x+4)-(x+4)=0 which is same as
3x^2(x+4)+(-1)(x+4)=0
(3x^2-1)(x+4)=0
3x^2-1=0
3x^2=1
x^2=1/3
x= +-1/3

and

x+4=0
x=-4