Let $A = \mathbb{Q}[X]/(X^3-1)$.
- Prove that $A$ is a direct product of two integral domain;
- Is the ring $A$ isomorphic to $\mathbb{Q}[X]/(X^3+1)$? Justify your answer.
My idea: For question 1, $$ x^3-1 = (x-1)(x^2+x+1),$$ so$$\mathbb{Q}[x]/(x^3-1) = \mathbb{Q}[x]/(x-1) × \mathbb{Q}[x]/(x^2+x+1).$$
For question 2, yes, $A$ isomorphic to $\mathbb{Q}[x]/(x^3+1)$.
Is it correct?