00:01
So we need to show that matrix a, b, c, d has, or is the identity matrix.
00:06
So we're going to go through the matrix multiplication first.
00:09
So we're going to multiply across and down.
00:12
So 0 .4a plus 0 .6c, 0 .3a plus 0 .2c.
00:20
And then we're going to do the same thing with the second column.
00:25
So 0 .4b plus 0 .6.
00:30
D, 0 .3b, plus 0 .2d.
00:37
And this will be equal to the matrix that has 0 .4, 0 .6, 0 .3, and 0 .2.
00:47
So we're going to write a system of equations.
00:49
The 0 .4a plus 0 .6c is equal to 0 .4 .0 .3a plus 0 .2c2c, is equal to 0 .3.
01:03
We're going to write the other set of equations 0 .4b plus 0 .6d.
01:10
0 .3b plus 0 .2d is equal to 0 .2.
01:16
And the top one there is equal to 0 .6.
01:20
Solving these equations, we're going to need to, we'll focus on the one that has a and c first.
01:27
Okay.
01:29
We need to figure out a variable to eliminate, let's choose to eliminate the c first, so i'm going to multiply the bottom equation by negative 3.
01:37
So the top equation stays the same...