יהי ${\displaystyle U=span\left[{\begin{array}{c}1\\0\\-1\\-2\end{array}}\right],\left[{\begin{array}{c}-1\\-1\\0\\2\end{array}}\right],\left[{\begin{array}{c}1\\2\\1\\-2\end{array}}\right]}$ ו-${\displaystyle W={\begin{cases}\left[{\begin{array}{c}x_{1}\\x_{2}\\x_{3}\\x_{4}\end{array}}\right]\in \mathbb {R} ^{4}|{\begin{array}{c}x_{1}+3x_{2}+x-3-x_{4}=0\\x_{2}-3x_{3}+2x_{4}=0\end{array}}\end{cases}}}$

מצא את בסיס החיתוך של ${\displaystyle U,W}$.