[tex]\it x\in\mathbb{Z}_4 \Rightarrow x\in\{\hat 0,\ \hat1,\ \hat2,\ \hat3\}|_{\cdot2} \Rightarrow 2x\in\{\hat0,\ \hat2\}|_{+1} \Rightarrow2x+1\in\{\hat1,\ \hat3\} \Rightarrow\\ \\ \Rightarrow\ ecua\c{\it t}ia\ 2x+1=0\ nu \ are\ nici\ o \ solu\c{\it t}ie\ \^{i}n\ \mathbb{Z}_4[/tex]
