2. Consider the matrices A and B: A=\left[\begin{array}{rr} 1 & 1 \\ -1 & -1 \end{array}\right] \quad B=\left[\begin{array}{rr} k^{2} & 3 \\ 4 & 6 \end{array}\right] (a) Find A-1 and

B-1, and if either is undefined, explain why: (b) Find A + В -2 (c) Find all k such that B is invertible: (d) Find B+ A999 :