Linear programming: writing a problem with artificial variables?

Use artificial variables to write a linear programming problem in canonical form with non-negative resource vector whose solution will determine whether there exists (and if so, find) non-negative reals $x1, x2, x3,$ and $x4$ such that $x1-x2+x3+x4=1$ and $x_1\begin{bmatrix}0 \\ 1\end{bmatrix} + x_2\begin{bmatrix}-2 \\ 0\end{bmatrix} + x_3\begin{bmatrix}1 \\ -2\end{bmatrix} + x_4\begin{bmatrix}0 \\ -1\end{bmatrix} = \begin{bmatrix}1 \\ -1\end{bmatrix}$. After setting up the problem, use the simplex method to solve it.

Can someone help me with this question? I'm not sure what it's exactly asking and I don't know how to approach it. I thought that the above two equations are the constraints?

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I'm a bit confused by the question, too. Perhaps you could ask your professor? –  Mike Spivey Dec 17 '12 at 3:59