00:01
In this problem, we're trying to find the inverse of a.
00:05
And using what we know about matrix properties, we can say that a times its inverse is equal to the identity matrix i, which is 1 -0 -0 -1.
00:18
And so using this formula, we can write out the equation.
00:22
So a is equal to 1, negative 5, 0, and negative 4 times the inverse of a, which we don't know.
00:30
Know, but we can write out as variables for now is equal to 1 .001.
00:38
So our first step is going to be to multiply out the left -hand side of the equation.
00:44
And that is going to result in a 2 -2 matrix with the first entry being the first row multiplied by the first column of the second matrix.
00:54
So a minus 5c.
00:59
Our second entry is going to be the first row.
01:02
Row multiplied by the second column, so b minus 5d.
01:08
Our third entry is going to be our bottom row here, multiplied by our first column, so 0a minus 4c.
01:18
And our fourth entry is going to be our last column, multiplied by our last row, so b0b minus 4d.
01:28
And that is equal to 1 ,001.
01:33
And so taking this matrix and simplifying it down a little bit, we get that a minus 5c, b minus 5d, and then negative 4d here and negative 4c is equal to 1 .01...