00:01
Okay, this is general form of an equation of a circle, so we want to put it in standard form, which means we'll be able to tell exactly where it is and how big it is.
00:11
So to do that, we're going to have to complete the square.
00:13
So here's what you do.
00:15
You put the x pieces together plus a blank, where you're going to complete the square.
00:22
You put the y pieces together plus a blank, we're going to complete the square.
00:29
And you move the 11 over, and then you get rid of all that so i can do what i'm supposed to do here.
00:40
Add a blank, which is this blank, and a blank which is this blank.
00:48
Okay, so to complete the square, you take half of minus 8 and square it.
00:54
That's minus 4, so that's 16.
00:59
Half of minus 6 squared.
01:04
That's 9.
01:08
Okay, so then x squared minus 8, x plus 16 factors into x minus 1.
01:12
Minus 4 squared because that's minus 4.
01:17
And this factors into y minus 3 squared, because that's minus 3.
01:23
And this gives you 36 over there.
01:28
Okay, standard form is x minus h squared plus y minus k squared equals r squared.
01:39
Hk is the center.
01:41
So in yours, the center is 4 3.
01:46
R squared is 36, so the radius is 6.
01:49
Okay, so let's see if we can draw that.
01:55
It won't be very good.
01:57
Let's just pretend.
01:58
One, two, three, four, one, two, three, three, one, two, three, four, three, three, five, six.
02:04
The radius is six, one, two, three, four, five, six.
02:10
One, two, three, four, five, six...