# Rearrange equarion to make r the subject?!!

#### megc

##### New member
Hi, I would be massively grateful if someone could help me rearrange the following equation to make r the subject.

r+s = r-s
8s 8n

Many many thanks for any pointers in the right direction.

#### stapel

##### Super Moderator
Staff member
Hi, I would be massively grateful if someone could help me rearrange the following equation to make r the subject.

r+s = r-s
8s 8n

Many many thanks for any pointers in the right direction.
Trying to format with blank spaces, most of which are stripped out by the forum's back-end script, tends not to work very well. To learn how to format math as text, try here. In your case, the standard formatted would be:

. . . . .(r + s)/(8s) = (r - s)/(8n)

...which typesets as:

. . . . .$$\displaystyle \dfrac{r\, +\, s}{8s}\, =\, \dfrac{r\, -\, s}{8n}$$

A good start for solving would probably be to divide both sides by 8, and then multiply through to clear the denominators. This gives you:

. . . . .$$\displaystyle rn\, +\, sn\, =\, rs\, -\, s^2$$

Get the terms containing the desired variables on one side, with everything else on the other. Then (here's the trick) factor out the variable, and divide through. :wink:

#### megc

##### New member
Thank you very much for your advice and pointer in the right direction!