c) \(\Rightarrow\left(x+3\right)+14⋮\left(x+3\right)\Rightarrow\left(x+3\right)\inƯ\left(14\right)=\left\{-14;-7;-2;-1;1;2;7;14\right\}\)
\(\Rightarrow x\in\left\{-17;-10;-5;-4;-2;-1;4;11\right\}\)
d) \(\Rightarrow\left\{{}\begin{matrix}400⋮x\\300⋮x\end{matrix}\right.\) \(\Rightarrow x\inƯC\left(300;400\right)=\left\{100;50;2;...\right\}\)