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Math Help - changing the subject of a formula

  1. #1
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    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
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  2. #2
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    Re: changing the subject of a formula

    \displaystyle \begin{align*} 5 - a\,x &= b \\ -a\,x &= b - 5 \\ a\,x &= 5 - b \\ x &= \frac{5 - b}{a} \end{align*}
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  3. #3
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    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
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    Re: changing the subject of a formula

    Quote Originally Posted by davellew69 View Post
    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.
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  5. #5
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    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
    Last edited by davellew69; March 7th 2013 at 01:37 AM.
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