From Artin algebra books. chapter 13 Quadratic Number field
For which negative integer $d\equiv 2\mod4 $ is the rings of integer in $\mathbb{Q}(\sqrt d)$ a unique factorization domain.
My works : i know that integer R in $\mathbb{Q}(\sqrt d)$are of the form $a +b \sqrt d$ for $a,b \in \mathbb{Z}$
i thinks $d= -6$ or may be $d=0$
Am i right/wrong ?
Any hints/solution will be appreciated .
thanks u