$\begin{array}{l}
A = \left\{ {x \in \mathbb{Z}| - 1 < x < 3} \right\}\\
\Rightarrow A = \left\{ { - 2; - 1;0;1;2} \right\}\left( {do\,x \in \mathbb{Z}} \right)\\
B = \left\{ {x \in \mathbb{N}|x < 4} \right\}\\
\Rightarrow B = \left\{ {0;1;2;3} \right\}\\
\Rightarrow A\backslash B = \left\{ { - 2; - 1} \right\}
\end{array}$