Để \(B=\frac{-3}{1+\sqrt{x}}\in Z\Leftrightarrow B=\frac{-3}{1}+\frac{-3}{\sqrt{x}}=-3+-\frac{3}{\sqrt{x}}\in Z.\)
Mà \(-3\in Z\Rightarrow\frac{-3}{\sqrt{x}}\in Z\)
\(\Rightarrow-\sqrt{x}\inƯ_3=\left\{1;3\right\}\)
\(\Rightarrow-x=\left\{1;9\right\}\)
\(\Rightarrow x=\left\{-1;-49\right\}\)