00:01
So i see that you need help with this problem.
00:02
And so i have the equations of x plus 2y plus 4z equals 9.
00:08
Then i have 2x plus 2y plus 3z equals 8.
00:19
Then i have x minus y plus z equals 3.
00:31
And what i'm going to do is i will solve for z first.
00:36
So i have z equals negative x plus z equals negative x plus y plus 3.
00:55
So i'm going to plug this into both of these equations here.
00:59
So x plus 2y plus 4 times negative x plus y plus 3 equals 9.
01:08
And then i have 2 times x plus 2y plus 3 times negative x plus y plus 3 equals 8.
01:21
So i have x plus 2y minus 4x plus 4y plus 12 equals 9.
01:35
And then i'm going to combine terms that are alike.
01:39
So i have this x and this negative 4x, which is negative 3x.
01:44
This 2y and 4y, which equals plus 6y, equals and then 12 minus 9, which is going to be that negative 3...