00:01
So we're told for any matrix c that c cubed is equal to zero, and we're trying to show that i minus c is invertable by showing in other words that has an inverse, that i minus c inverse is actually this.
00:19
It's i plus c plus c squared.
00:22
To show this, i need to show that i minus c multiplied by this, i plus c squared, is going to give.
00:32
Me the identity matrix.
00:36
And if you recognize this, and i hope you do, that is a difference of q.
00:39
So what i'm going to end up with is just i squared, okay, and then plus i times c, and then plus i times c squared, and then minus c times i, minus c squared, minus c cube.
01:04
Okay, that's what we're going to end up with if we multiply it all out.
01:07
And what's going to happen is that i'm going to get i squared, which is just the identity matrix, i times c minus c times i...