# Homework Help: Radius of Circle

1. May 6, 2009

### imdapolak

1. What are the radius and center of this circle? x^2+4x+y^2-3y=0

2. Relevant equations

3. Another question on my final review I dont recall exactly how to set up or what steps I need to do in order to solve this problem. Any help is appreciated

2. May 6, 2009

### gabbagabbahey

If I gave you the equation in the form $(x-a)^2+(y-b)^2=r^2$, could you tell me the location of the center of the circle and its radius?

If so, just complete the square for both x and y in your above equation in order to get it into this form.

3. May 6, 2009

### Cyosis

The equation of a circle is of the form (x-a)^2+(y-b)^2=r^2. So you want to write x^2+4x as (x-a)^2+constant. In other words complete the square.