Question 73727
If we look at the roots of x(x+1)(x-4) we get x=0, x=-1, and x=4. At the roots the graph of f(x) goes from either a positive number to a negative number or from a negative number to a positive number. At this point we only care about the positive portion. So if we graph x(x+1)(x-4) we get
{{{graph( 300, 200, -3, 5, -10, 10, x*(x+1)*(x-4)) }}}
So the roots are the endpoints where the interval is
[-1,0]U[4,{{{infinity}}}) Which can be easily obtained from the graph.