Question 765963
That's exactly the polynomial you're looking for! Maybe you are supposed to work it out, like
{{{(x+2)(x-3)(x-3)(x+1)=(x^2-x-6)(x-3)(x+1)=(x^3-x^2-6x-3x^2+3x+18)(x+1)=(x^3-4x^2-3x+18)(x+1)=x^4-4x^3-3x^2+18x+x^3-4x^2-3x+18=x^4-3x^3-7x^2+15x+18}}}


But the answer you gave is exactly the right way to solve this problem.