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Square Root Method

  1. Sep 21, 2009 #1
    1. The problem statement, all variables and given/known data
    (x - 1)^2 = 4

    3. The attempt at a solution
    This is what I've done

    (x - 1)^2 = 4

    Everything inside parenthesis goes to: ^2
    x^2 - 1^2 = 4

    now we got
    x^2 - 1 = 4

    Now (I think) I use the square root method
    x^2 - 1 = √4
    x^2 - 1 = 2

    Now I factorize:
    (x - 1) (x +1) = 2

    This is what I've done for now, shall I make √ on both sides in this equation x^2 - 1 = √4?
     
  2. jcsd
  3. Sep 21, 2009 #2

    rock.freak667

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    Homework Helper

    (x-1)2≠x2-1

    (a+b)2=a2+b2+2ab

    you can also take the square root initially and check the two cases

    X2=A => X=±√A i.e. X= +√A or X=-√A
     
  4. Sep 21, 2009 #3
    Thanks, All I did now is use the square root right on start:

    √(x - 1)^2 = √4

    So now we go this:

    x - 1 = ±2

    which gives me the following results:

    x - 1 = ±2
    x = 2 + 1
    x = 3

    OR

    x - 1 = ±2
    x = -2 + 1
    x = -1
     
  5. Sep 21, 2009 #4

    rock.freak667

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    Homework Helper

    Good. This is correct because if we put x=3 or x=-1 into (x-1)2, we ill get '4'.
     
  6. Sep 21, 2009 #5
    Thanks!
     
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