QUESTION 3
3.1 Let the vectors w, x, y and z be given by
$$w = \begin{pmatrix} 1 \\ 1 \\ 1 \\ 1 \end{pmatrix}, x = \begin{pmatrix} 1 \\ -2 \\ 0 \\ 0 \end{pmatrix}, y = \begin{pmatrix} 1 \\ 0 \\ 0 \\ 0 \end{pmatrix}, z = \begin{pmatrix} 1 \\ 1 \\ 1 \\ -3 \end{pmatrix}$$
Find the Moore-Penrose inverse of the matrix
$$A = wx' + yz.$$
3.2 Let A be an m x m matrix partitioned as
$$A = \begin{bmatrix} A_{11} & A_{12} \\ A_{21} & A_{22} \end{bmatrix},$$ where $A_{11}$ is r x r.
Show that if rank (A) = rank ($A_{11}$) = r, then
$$\begin{bmatrix} A_{11}^{-1} & 0 \\ 0 & 0 \end{bmatrix}$$
is a generalized inverse of A.
3.3 Find a generalized inverse of the matrix
$$A = \begin{bmatrix} 1 & -1 & -1 & -2 \\ -2 & 4 & 4 & 3 \\ 1 & 1 & 1 & -3 \end{bmatrix}.$$
[19 Marks]
(6)
(6)
(7)