# changing the subject of a formula

• Mar 7th 2013, 01:16 AM
davellew69
changing the subject of a formula
hi, Im a bit puzzled on a question and answer

I have 5-ax=b and I have to make x the subject. The given answer is x=5-b/a but Im not getting how this is achived

Dave
• Mar 7th 2013, 01:19 AM
Prove It
Re: changing the subject of a formula
\displaystyle \displaystyle \begin{align*} 5 - a\,x &= b \\ -a\,x &= b - 5 \\ a\,x &= 5 - b \\ x &= \frac{5 - b}{a} \end{align*}
• Mar 7th 2013, 01:23 AM
davellew69
Re: changing the subject of a formula
thanks, just two questions from -ax=b-5 why does the a lose its - and why is b-5 switched around?

Dave
• Mar 7th 2013, 01:24 AM
Prove It
Re: changing the subject of a formula
Quote:

Originally Posted by davellew69
thanks, just two questions from -ax=b-5 why does the a lose its - and why is b-5 switched around?

Dave

Multiply both sides by -1, then distribute.
• Mar 7th 2013, 01:27 AM
davellew69
Re: changing the subject of a formula
can you explain why you multiply both side by -1 and what is meant by distriute? by multiplying both side by -1 would that not make b+5

dave