how to (please help)?

Question

how do you find the radius of a circle with the equation

x2 + y2 - 2y = 3.

thanks so much!!

x2= x squared
y2= y squared

Answer 1

x2 + y2 - 2y = 3 where
x2= x squared
y2= y squared

Step 1) Use the completing the square method.

x2 + (y2 - 2y + __) = 3 + __
Half it, square it
x2 + (y2 - 2y + 1) = 3 + 1
Simplify:
x2 + (y-1)2 = 4


Step 2) Find the radius

Use x2 + y2 = r2,
where r = radius
x2 + (y-1)2 = 4
4 = r2
r=2 since you can't have a negative radius length

Answer 2

You must complete the square. When you complete the square for the y term, you get x^2 + y^2 - 2y + 1 = x^2 + (y-1)^2 = 3 + 1 = 4. Thus, the radius is sqrt{4} = 2.

Answer 3

Complete the square in y:
x^2+ y^2 -2y +1 = 3 + 1
x^2 +(y-1)^2= 4 = 2 ^2
The radius is 2 and the center is at (0,1)