Question

tim n biet (7n + 9 ) chia het cho ( n + 2 )

Answer 1

\(7n+9⋮n+2\)

\(\Rightarrow7n+14-5⋮n+2\)

\(\Rightarrow7\left(n+2\right)-5⋮n+2\)

      \(7\left(n+2\right)⋮n+2\)

\(\Rightarrow5⋮n+2\)

\(\Rightarrow n+2\in\left\{-1;1;-5;5\right\}\)

\(\Rightarrow n\in\left\{-3;-1;-7;3\right\}\)

Answer 2

\(7n+9⋮n+2\)

\(\Rightarrow7\left(n+2\right)-5⋮n+2\)

Do\(7\left(n+2\right)⋮n+2\Rightarrow5⋮n+2\)

\(\Rightarrow n+2\inƯ\left(5\right)\)

\(\Rightarrow n+2\in\left\{5,1,-5,-1\right\}\)

\(\Rightarrow n\in\left\{3,-1,-7,-3\right\}\)