00:02
We want to show that if a x equals 0 has only the trivial solution, trivial solution, then we want to show that a x equals b must have a solution for every b.
00:45
Now the way to do it without the invertible, matrix theorem is to observe the structure of a.
00:54
So we consider, let's consider the reduced row -ishlan form of a, say, a prime.
01:11
Okay, so excuse me, so that means a prime times x equals zero.
01:24
This system has no free variable.
01:29
Because this system has only trivial solution.
01:35
That means the system has no free variable because we know from our previous material, we know that the system has non -trivial solution if it has at least one free variable.
01:48
So it's just a negation of the segment.
01:50
So i'll just write down here just for your information.
01:55
A prime x times a prime x equals 0, has only trivial solution is equivalent to say that this system has no free variable, no free variable.
02:30
So furthermore, that means matrix a has n -pivaled positions.
02:44
Of course, we're assuming matrix a has an -pivaled positions.
02:49
This is our assumption.
02:53
Pivot positions, excuse me, people positions, and this is our conclusion here...