00:01
In this problem, we are going to use matrix algebra to solve for x and y.
00:04
And our first step in doing this is going to be to write all our coefficients in a matrix.
00:08
And so we get 4, negative 9, negative 1, 7, negative 3, 5 halves.
00:17
Now this matrix on the left hand side here, we're going to find the inverse of, and then we're going to multiply that by the matrix on the right here in order to get our x and y.
00:26
Now to find the inverse of this one on the left, i'm going to take 1 over, ad minus bc, so a times d is 4 times negative 3 or negative 12, minus negative 9 times 7, which is negative 63, so minus negative 63, and then times we're going to switch a and d, so negative 3 and 4, and make b and c negative.
00:50
So 9 and negative 7.
00:53
Now negative 12 plus 63, it is 51, or 1 over 51.
01:03
And so i get 1 over 51 times negative 3, 9, negative 7, 4.
01:13
Which, if i distribute 1 over 51 into every component, i get negative 3 over 51, 9 over 51, negative 7 over 51, and 4 over 51.
01:28
And now i'm going to multiply that by, again, this matrix on the right here, which is negative 1 and 5...