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Homework Help: Rearrange the formula

  1. Mar 2, 2010 #1
    I need to rearrange this formula to make e the subject. Have I done it correctly?

    10b + 5be - 3e + 7c
    10b + 5be - 3e = 7c
    5be - 3e = 7c - 10b
    e(5b - 3) = 7c - 10b

    e = 7c - 10b / 5b - 3
     
  2. jcsd
  3. Mar 2, 2010 #2

    Mark44

    Staff: Mentor

    You're not starting with an equation! Without the first line below being an equation, you can't solve for anything.
    Assuming that this is your starting equation -- 10b + 5be - 3e = 7c -- your work following it is fine, EXCEPT that you need to use parentheses. You should write e this way:
    e = (7c - 10b) / (5b - 3)
     
  4. Mar 2, 2010 #3
    Thanks a lot Mark
     
  5. Mar 3, 2010 #4
    Well if we assume that the first line is an equation (set equal to zero): 10b + 5be - 3e + 7c=0, then the second line changes:

    10b + 5be - 3e = -7c, and that would change the rest of the steps which follow...
     
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