So you mean: [tex]
f(x)=2x^4+3x^2- \frac{1}{3} x-3x^3
[/tex]
This isn't possible the function is defined for 1, -1 and 0 and the exercise says that that isn't possible.
What method did they use to get the solution other than just trying different order of polynomials? Can you give me the website where you got this?