Chapter 3.2, Problem 7EQ

In Exercises 5-8, write B as a linear combination of the other matrices, if possible.

$B=\left[\begin{array}{ccc}3& 1& 1\\ 0& 1& 1\\ & & \end{array}\right],A_1=\left[\begin{array}{ccc}1& 0& -1\\ 0& 1& 0\\ & & \end{array}\right]$

$A_2=\left[\begin{array}{ccc}-1& 2& 0\\ 0& 1& 0\\ & & \end{array}\right],A_3=\left[\begin{array}{ccc}1& 1& 1\\ 0& 0& 0\\ & & \end{array}\right]$