Recall that we can factorize any polynomial as:
[tex]P(x)=k(x-a)(x-b)...(x-n),[/tex]where k is a constant and a,b,...n are the root of the polynomial.
Therefore, a polynomial function with the real zeros -3,0, and 3 is:
[tex]f(x)=k(x-3)(x-0)(x+3).[/tex]k can be any constant, therefore, we can set k=1.