1. (10%) Let $$u1 = \begin{bmatrix} 1 \\ 0 \\ -1 \end{bmatrix}, u2 = \begin{bmatrix} 1 \\ 2 \\ 1 \end{bmatrix}, u3 = \begin{bmatrix} -1 \\ 1 \\ 1 \end{bmatrix}, b1 = \begin{bmatrix} 1 \\ -1 \end{bmatrix}, b2 = \begin{bmatrix} 2 \\ -1 \end{bmatrix}$$. Let L be the linear transformation defined by $$L(x1, x2, x3) =$$

$$(x1+x2, x1-x3)$$. Find the matrix A representing L with respect to the bases $$\{u1, u2, u3\}$$ and $$\{b1, b_2\}$$.