[tex]\it n+1|2n+11 \ \ \ \ \ (1)
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n+1|n+1 \Rightarrow n+1|(n+1)\cdot2 \Rightarrow n+1| 2n+2 \ \ \ \ (2)
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(1), (2) \Rightarrow n+1| 2n+11-2n-2 \Rightarrow n+1|9 \Rightarrow
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\Rightarrow n+1\in \{1,\ 3,\ 9\}|_{-1} \Rightarrow n\in \{0,\ 2,\ 8\} [/tex]
