# rearrange to make x the subject?

• February 21st 2011, 07:18 AM
andyboy179
rearrange to make x the subject?
hi,
i need to rearrange to make x the subject, the question is below with my workings of what i think could work:

Attachment 20891

basically i expanded the brackets and divided by what number y was. =y and -y cancel out to leave you with 0.5x=x

would this be correct? if not where am i going wrong? and can you help me to make this correct?

thanks!
• February 21st 2011, 07:22 AM
Prove It
The problem is that when you have been doing something to one side of the equation, you haven't done the same thing to the other side.

You are correct up to $\displaystyle 3x+6y=2x-2y$.

Now you need to collect all $\displaystyle x$ terms on one side and all $\displaystyle y$ terms on the other side...

$\displaystyle 3x + 6y - 2x = 2x - 2y -2x$

$\displaystyle x + 6y = -2y$.

Now how would you collect all the $\displaystyle y$ terms to the right hand side?
• February 21st 2011, 07:25 AM
andyboy179
so that would be x=-8y
• February 21st 2011, 07:27 AM
Prove It
Correct.
• February 21st 2011, 07:28 AM
andyboy179
oh so now they are on their seperate sides x=-8y is the answer. i understand! thanks!!