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Homework Help: Rearrange formula

  1. Dec 7, 2009 #1
    I have been trying to rearrange this formula to make x the subject:

    ax - b = cx + d

    My (wrong) attempt at the answer was:

    x = cx + d/a - b

    I know that that is wrong because x still appears on the right side of the formula. The right answer is:

    x = (d+b)/(a-c)

    I have no idea how to arrive at that. Can anyone talk me through it step by step?
  2. jcsd
  3. Dec 7, 2009 #2
    sure: first collect all the x terms on one side by subtracting cx from both sides:


    now collect all the non x terms on the opposite side by adding b to both sides.

    ax-cx=b+d now factor out x so that it looks like x(a-c). Divide both sides by what now?
  4. Dec 7, 2009 #3
    Divide both sides by (a-c) and you get:
    x = (d+b) / (a-c)
    Thanks a lot Denverdoc!! It was very kind of you to help out.
  5. Dec 7, 2009 #4
    no problem; btw there is a math forum here for various issues you may run into. fine that you posted here, but in future may wish to consider it.
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