I have this function : $\displaystyle f(x)=x^3-x^2+4x-3$

I need to find the intervals of increase and decrease so i have to factor the first derivative of that function which is $\displaystyle f'(x)=3x^2-2x+4$

Now i need to as it says here...put the first derivative equal to zero. But the problem being is that you can't really factor this regularly...so you have to use the quadratic equation. Am I able to use quadratic formulae? for the zeros that I need to find?