I am not sure exactly what this question is asking:

Determine the following groups of units:

a) U(Z[x]) where Z[x] is all polynomials with integer coefficients

b) U(Z[i]) where Z[i] is the gaussian integers (a+bi)

c) U(R[x]) where R[x] is all polynomials with real coefficients

I think this means find which elements in these groups have inverses

I am not quite sure but I have:

a) 1,-1

b) 1,-1,i,-i

c) 1,-1

Thoughts?