Zeige, dass das Polynom X 3 + 2 X 2 − 5 {\displaystyle {}X^{3}+2X^{2}-5} in Q [ X ] {\displaystyle {}\mathbb {Q} [X]} irreduzibel ist.
![{\displaystyle {}\mathbb {Q} [X]}](https://wikimedia.org/api/rest_v1/media/math/render/svg/05854fb7f5090d865105d7297fa178c8eb802fbf)