You are Here: Home >< Maths

# How to give the equation of a circle

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
1. I'm doing EDEXCEL A level maths and for my C2 exam there's going to be at least 1 question where I have to work out the equation of a circle. Usually I will work it out and give my final answer as x^2+y^2-ax-by-c=0 but usually in exam mark schemes the answer is given as (x-a)^2 + (y-b)^2 = r^2 . I understand that the two are identical but just written differently but does it matter which one I write if they both man the same?

Thanks
2. I'd go for the second one.
3. They will want it in the form (x-a)^2 + (y-b)^2 = r^2

Do you know how to convert your form to the above?
4. Yeah thanks. I usually work it out and get my answer in that form then change it to one polynomial
5. (Original post by maxcharlish)
I'm doing EDEXCEL A level maths and for my C2 exam there's going to be at least 1 question where I have to work out the equation of a circle. Usually I will work it out and give my final answer as x^2+y^2-ax-by-c=0 but usually in exam mark schemes the answer is given as (x-a)^2 + (y-b)^2 = r^2 . I understand that the two are identical but just written differently but does it matter which one I write if they both man the same?

Thanks
Unless the format is specified in the question it doesn't matter. You are wasting exam time by taking the standard format and expanding the brackets. As soon as they see the (x-a)^2 + (y-b)^2 = r^2 they will award the marks and ignore your subsequent working.

Posted from TSR Mobile

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: May 8, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams