00:01
Okay, so you want abc to be to be a row equivalent to 1 ,000.
00:17
So in particular, note that this has rank 1.
00:23
So, so basically your initial matrix also has to be rank 1.
00:30
So what does rank 1 mean? it means that if you have a 2 by 2, it means that the rows must be linearly dependent.
00:38
That means that the vector ab and vector cd are linearly dependent.
00:52
And what does this mean when you only have two sets of vector? this means that in particular, ab has to equal a constant times cd.
01:08
So one condition you have is that you must have, i guess, okay, so you must have c.
01:20
Equal i'm gonna i'm gonna put the constant on this since i want to keep looking at the a and b is equal to the constant times ab so this is one condition so if you have this then you can row reduce by multiplying by just doing row two you transform row two by taking row two minus k row one then you can row reduce and you get to a, b, zero, zero.
01:59
And now, how do you get to having zero here? you actually can't, unless one of these is going to be zero.
02:12
So what you also need is that you need one of these matrices to have zero.
02:30
And specifically, you want b to have value zero.
02:33
So you need b is equal to zero.
02:35
Because if it weren't zero, then it would still be kept alive by this row reduction you've done...