What are the value(s) of k?

Question

let A = [ 3 2

-1 2]

B = [ 2 8

-4 k]

What values(s) of k, if any, will make AB=BA?

a) k = []

b) No value of k will make AB = BA

Answer 1

The product of AB is

| -2 24+k |

| -10 -8+2k |

The product of BA is

| -2 20 |

| -12-k -8+2k|

The condition AB=BA is satisfied by k=-2

Best,

Davide