00:01
In this exercise, we want to use kramer's rule to solve the system.
00:03
So let's start with the matrix that's going to make up our denominator.
00:06
So we just use the coefficients that we're given.
00:08
0 .4, 1 .2, 1 .2, 1 .6.
00:14
So this is going to be 0 .4 times 1 .6.
00:17
I think it's easier to think about these in terms of fractions.
00:19
It's going to be 4 over 10 times 16 over 10 minus 1 .2 times 1 .2 .2.
00:27
I think that's just 12 over 10 times 12 over 10, which is 1 .4.
00:30
44 over 10.
00:33
So we get our 100 by that.
00:34
So four times 16 is going to be 64 over a hundred here.
00:39
We've got minus 144 over 100.
00:42
And we see that's going to give us negative 80 over 100.
00:47
So that's just negative 8 over 10.
00:50
Now the numerator for x, we're going to replace the x column with our constants, 0 .4.
00:58
I'm just going to write them as the fraction.
00:59
0 .4.
01:00
So that's 4 over 10.
01:01
3 .2, which is 32 over 10.
01:04
And then we're going to leave our y, so that's 12 over 10, and 16 over 10.
01:10
So now we've got 4 times 16 over 100, so that's 64 over 100, minus 32 times 12 over 100.
01:20
So we're going to come back to that.
01:21
It's kind of ugly just to do on top of our heads.
01:24
And then y numerator is going to equal.
01:28
We're going to keep the x, so it's 4 over 10, 12 over 10, and then we're going to replace the y with the constants 4 over 10 and 32 over 10.
01:41
So we've got 4 over 10 times 32 over 10.
01:44
That's going to give us 64 times 2, which is 128...