00:01
Okay, let's take a look at this system of three equations.
00:04
Now, i'll number them one, two, three, so you know which ones i'm talking about.
00:09
I'm going to start with two and three, and i like those two because i see that z and that negative z in two and three.
00:16
It's not the only choice for how to start this problem, it's just one option.
00:21
So here's those two equations as written.
00:24
I'm going to add them up, and when i do those zs, we'll cancel out.
00:28
So that's going to leave me with 7x plus y equals 0.
00:34
Now, i have to use equation 1.
00:38
So i can combine it with either of the other 2.
00:41
I'm just going to do 1 and 2.
00:43
So here they are, as written.
00:47
And again, i want those zs to cancel out.
00:50
So i'm going to multiply this bottom equation by 2.
00:54
So the top equation would stay the same.
00:57
The bottom equation would now be 6x minus 2y plus 2 z equals 0.
01:07
Let's add these two equations.
01:10
I get 7x minus y, z's cancel out, and it equals 0.
01:19
Now i have two equations, both in terms of x and y.
01:23
So let's deal with those two.
01:26
Again, i'm going to add them...