7. For each of the following matrices, find the inverse or show that the matrix is not

invertible. Explain your reasoning. (You need to show your steps, however, you can

skip the details of EROS.)

(a) A =

(b) B

- 21

(c) C

=

12

[1 1 2]

23

-1

SEN

[102]

(d) D = 1 1 3

3 17