00:01
Okay, so for this one, we need to put three equations into a matrices.
00:04
So we're going to start by making three equations.
00:08
So first we know that the amount borrowed adds up to $30 ,000.
00:14
So we want to know the amount borrowed for each one of these interest rates.
00:20
So a, so we're going to be our first one, plus b, plus c equals $30 ,000.
00:28
Then we're going to find the amount borrowed at each.
00:31
So we know the interest rate is $3040, and it gives us the interest.
00:39
So the interest rate of the first one is .08, so we're going to take .08 of the money borrowed, plus .1 of the money borrowed, plus .12 of the money borrowed.
00:53
Okay, so that's our second equation.
00:56
Lastly, we have that we know the first two add together to be, sorry, a plus b, those add to be greater than the third one.
01:09
So we're going to take 2 times c.
01:12
Okay, we need to solve that equation, the last one, to make all the variables on the same side.
01:18
So we're going to subtract 2c over, so a plus b minus 2c equals 0.
01:25
Okay, now we can go ahead and put this in the matrix.
01:30
So when we do this, we look at the numbers in front of our variables.
01:35
So we have 1, 1, 1, 30 ,000, .08, .1, .12, 3040, then 1, 1, negative 2, 0.
01:59
All right, now we're going to go ahead and solve this matrix.
02:02
So we're going to do reduced row echelon.
02:08
So here we're going to take our row 2.
02:12
That is going to be row 2 minus .8 of row 1.
02:24
Okay, we're going to go ahead and make our new matrix using this rule.
02:36
So 1, 1, 1, 30 ,000.
02:40
We are only changing the second row with that rule.
02:54
Okay, so we're taking row 2 minus .8 times row 1.
02:59
All of row 1 is 1s, so that leaves us with 0.
03:04
I am going to do fractions here.
03:07
1 over 50, 1 over 25, 640.
03:13
Okay, third row stays the same.
03:19
All right, our next rule that we're going to do is we're going to subtract row 1 from row 3.
03:26
That's just going to change that third row.
03:41
Okay, new matrix.
03:43
The first two rows just stay the same.
03:47
0, 1 over 50, 1 over 25, 640.
03:58
Okay, when we do row 3 minus row 1, these both become 0s.
04:04
And then this becomes a negative 3 because it's 1 minus, um, sorry, negative 2 minus 1.
04:12
So negative 3.
04:15
Negative 30 ,000...