x = 7
( x + 11 ) ⋮ ( x + 2 ) = ( 7 +11) ⋮ ( 7 + 2 ) = 18 ⋮ 9
\(\left(x+11\right)⋮\left(x+2\right)\Rightarrow\left(x+2\right)+9⋮\left(x+2\right)\)
\(\Rightarrow\left(x+2\right)\inƯ\left(9\right)=\left\{-9;-3;-1;1;3;9\right\}\)
\(\Rightarrow x\in\left\{-11;-5;-3;-1;1;7\right\}\)
\(\Leftrightarrow x+2\in\left\{3;9\right\}\)
hay \(x\in\left\{1;7\right\}\)