1/ If $d$ is not a square in $\mathbb{Q}$, show that $\mathbb{Q}[\sqrt{d}]\approxeq\mathbb{Q}[X]/
2/ If $d_1, d_2$, and $d_1/d_2$ are not squares in $\mathbb{Q}\backslash\left\{ 0\right\} $, show that $\mathbb{Q}[\sqrt{d_1}]$ and $\mathbb{Q}[\sqrt{d_2}]$ are not isomorphic.
3/ Let $R_1 = \mathbb{Z}_5[X]/