By trial and error find examples of 2 by 2 matrices such that (a) A 2 = I, A having only
Chapter 1, Problem 1.4.13(choose chapter or problem)
By trial and error find examples of 2 by 2 matrices such that (a) A 2 = I, A having only real entries. (b) B 2 = 0, although B 6= 0. (c) CD = DC, not allowing the case CD = 0. (d) EF = 0, although no entries of E or F are zero.
Unfortunately, we don't have that question answered yet. But you can get it answered in just 5 hours by Logging in or Becoming a subscriber.
Becoming a subscriber
Or look for another answer