You are Here: Home >< Maths

# Rearrange the formula to make r the subject

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
1. A=4+r(squared)
2. A-4=r^2
(root)A-4=r
3. (Original post by questioner...)
A=4+r(squared)
A=4+ r2

Subtract 4 from both sidesA - 4 = r2

Square root both sides
√ (A-4) = r (Make sure the square root extends over the whole of A-4)

r= √(A-4)
4. (Original post by natalijka09)
A=4+r(squared)
A-4= r(squared)
(root)(A-4)= r
(root)A - 2= r
No full answers please. Especially none where you don't know how roots work.
5. If you do an operation on one side of an equation, that equation can only hold if the same operation occurs on the other. You need to 1. get an equation in terms of everything not r on one side, and everything r on the other, 2. reduce the equation to r= (something without r).

## 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: October 6, 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