00:01
In this example, we're going to let aba3 by two matrix.
00:10
Then let's consider the matrix equation, a times x equals the zero vector.
00:16
Let's also give this a particular condition.
00:19
Let's suppose that this equation has only the trivial solution.
00:29
Let's say next what this would mean specifically about our matrix a.
00:33
So we have if we have only the trivial solution that would then imply that the equation has no free variables.
00:50
But if there are no free variables that will then imply that the columns of a are all pivot columns.
01:06
So let's write down an example of such a matrix a.
01:10
It's going to have three rows, two columns, and we want to have only the trivial solution for this particular matrix a when we consider the homogeneous equation.
01:23
But this is really the key.
01:24
We just have to make sure the columns of a are all pivot columns.
01:27
So we could say put a 1 -0 -0, making this matrix a little bit simpler is a decent way to go.
01:35
We could also go 0 -20 if we want to get a little fancy and not use ones everywhere.
01:40
And for this particular matrix, this has two pivot columns, so it will satisfy the original condition...