Question

tìm n thuộc Z

a. 2n+8 thuộc B(n+1)

b. 3n-1 chia hết cho n-2

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Answer 1

\(2n+8⋮n+1\)

\(\Rightarrow2\left(n+1\right)+6⋮n+1\)

\(\Rightarrow6⋮n+1\Rightarrow n+1\inƯ\left(6\right)=\left\{\pm1;\pm2;\pm3;\pm6\right\}\)

\(\Rightarrow n\in\left\{0;-2;1;-3;2;-4;5;-7\right\}\)

Vậy............................

\(3n-1⋮n-2\)

\(\Rightarrow3\left(n-2\right)+5⋮n+2\)

\(\Rightarrow5⋮n+2\Rightarrow n+2\inƯ\left(5\right)=\left\{\pm1;\pm5\right\}\)

\(\Rightarrow n\in\left\{-2;-3;3;-7\right\}\)

Vậy.................................