00:01
Okay, so to find the center and the radius of the circle, the first step that we're going to want to do is to put this equation into standard 4.
00:11
So to do that, i'm going to add 16 to both sides.
00:15
So we're going to have x squared plus y squared minus 4y equals 16.
00:24
She brought the 16 from here over to this side.
00:28
And so now this y squared plus 4 y, we're going to complete the square.
00:34
Okay? and so to complete the square, you take half of your, of this term right here.
00:41
So you take minus four and you divide it by two, which equals minus two, and then you square that term.
00:50
So this case, minus two squared is equal to positive four.
00:53
And you add positive four to both sides of your equation.
00:56
So our new equation is going to be x squared plus y squared minus 4 y plus 4 equals.
01:08
And now we have to do 16 plus 4 also, which is going to be 20.
01:14
Okay, so that's called completing the square.
01:16
Just completed the square.
01:18
And so now we can find a number that multiplies to positive 4 and adds to minus 4.
01:26
We can do that, so we have x squared...