Finde in Q [ X ] / ( X 2 − 1 ) {\displaystyle {}\mathbb {Q} [X]/(X^{2}-1)} nichttriviale idempotente Elemente.
![{\displaystyle {}\mathbb {Q} [X]/(X^{2}-1)}](https://wikimedia.org/api/rest_v1/media/math/render/svg/6393e69dbe697946a71f6b58d570641b4d8132bc)