00:01
For number 21, i'm to solve this using elimination.
00:05
First time, i need to rearrange these so they line up.
00:08
I'm going to put them both in standard form.
00:11
I'm going to bring them down here.
00:16
So i want this to be the x, the y, and then equals the plain number.
00:21
So my x, i'm going to bring my 3x to this side to make it positive.
00:25
So this will be a positive 3x.
00:28
My 4y is already on this side.
00:34
And then my nine's already on that side.
00:38
So that's the first one.
00:40
The second one.
00:41
My x is already here.
00:46
My y i'm going to bring to this side, so that's going to make it positive.
00:50
So plus six way.
00:57
And my 16, i have to take it to the other side.
00:59
So i'm going to add 16 to both sides.
01:02
That's going to make this positive.
01:05
Okay.
01:05
Now that i'm lined up, i can tell what i need to do here.
01:08
I could either try to make my x is the same.
01:10
Maybe make them both.
01:12
Or i can make my y is the same, making both 12.
01:17
I think i'm going to do my x's.
01:20
So if i multiply this whole equation by 5, and if i multiply this whole equation by, i need to make it negative 3, so that i'll have a positive 15 here and a negative 15 here.
01:38
So i'm going to, i guess i'll just keep scrolling down here.
01:46
So i'm just going to multiply and move down here...