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A simple math equation solving for unknown

  1. Dec 19, 2012 #1
    1. The problem statement, all variables and given/known data

    Solve for A
    27 = 81/√3a-3

    2. Relevant equations



    3. The attempt at a solution

    Im not sure where to begin with this question. Can someone go through all the steps into solving for A. Thanks
     
  2. jcsd
  3. Dec 19, 2012 #2
    Is it sqrt(3a - 3) or sqrt(3a) - 3 or sqrt(3) * a - 3.

    Whatever value of "a" is in the denominator, it has to be moved to the numerator, usually by multiplying both sides of the equation by the appropriate term containing "a". If it's sqrt(3a - 3) then multiply both sides of the equation by sqrt (3a - 3) to get:

    27 * sqrt(3a - 3) = 81.

    Then continue to solve for "a".
     
  4. Dec 19, 2012 #3
    Multiply both sides by sqrt(3a-3). It should be pretty straightforward from there
    Edit:never mind someone else answered it first
     
  5. Dec 19, 2012 #4

    SammyS

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    Begin by using enough sets of parentheses to make the problem unambiguous.

    Is it

    [itex]\displaystyle 27=\frac{81}{\sqrt{3a-3\,}}[/itex]

    or

    [itex]\displaystyle 27=\frac{81}{\sqrt{3a\,}-3}[/itex]

    or

    [itex]\displaystyle 27=\frac{81}{\sqrt{3\,}\,a-3}[/itex]

    or

    [itex]\displaystyle 27=\frac{81}{\sqrt{3a\,}}-3[/itex]


    or what it means literally with there being no parentheses

    [itex]\displaystyle 27=\frac{81}{\sqrt{3\,}}a-3[/itex]

        ?
     
  6. Dec 19, 2012 #5
    yes I should have mentioned it is square root 3a-3 not square root 3a then minus 3. Ok thanks for the responses.
     
  7. Dec 19, 2012 #6
    ^the first example you gave sammy, how would I go through the steps to solve for A?
     
  8. Dec 19, 2012 #7

    SammyS

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    Isolate the radical.

    Square both sides.
     
  9. Dec 19, 2012 #8
    Ok, sorry Im not really math literate. How would you isolate the radical?
     
  10. Dec 19, 2012 #9
    ok so im gonna go through it.

    27 x √3a-3 = 81
    √3a-3 = 81/27
    √3a-3 = 3
    3a-3 = 9
    3a = 9 + 3
    3a = 12
    a = 12/3
    a = 4
     
  11. Dec 19, 2012 #10

    SammyS

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    Now, check your answer by plugging into the original problem.
     
  12. Dec 19, 2012 #11
    perfect...thank you very much sammy!
     
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