[tex]a) b|10\Rightarrow b\in D_{10}\\~~~~~~~~~ b\in \{1,2,5,10\}\\b) (b+3) |10\Rightarrow b+3\in D_{10}\\ ~~~~~~~~~~ b+3\in \{1,2,5,10\}\\~~~~~~~~~~ b\in \{-2,-1,2,7\}\\~~~~~~~~~~ b\in \mathbb{N}\Rightarrow b\in \{2,\7}\\c)b | (b+4)\\ b | b\\ .......... -\\ b | 4\Rightarrow b\in D_4\\ ~~~~~b\in \{1,2,4\}[/tex]
