Questions askedCategory: 2568Section 1.5 Exercise 56

How do the matrices that are given $A, B$ and $O$ relate to the equation? What is $X$?

Here $X$ is an unknown. What you need to do in this exercise is that you need to compute
$O^2-2O, A^2-2A, \text{ and } B^2-2B$
and show that all of them are equal to the zero matrix $O$.
The second part follows by noting that the matrix $B$ contains a variable $b$.