Y=X^1/2 is the same as Y=+/-sqrt(X) ?

  1. Y=X^1/2 is the same as Y=+/-sqrt(X) ??

    1. The problem statement, all variables and given/known data


    This is from a textbook:

    Y=X^1/2 is the same as Y=+/-sqrt(X)

    2. Relevant equations
    3. The attempt at a solution

    100^1/2=10

    How is 100^1/2=-10 also true?

    Thanks.
     
  2. jcsd
  3. tiny-tim

    tiny-tim 26,054
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    hi solve! :wink:
    you're right, it's wrong! :smile:

    (which book?)
     
  4. Re: Y=X^1/2 is the same as Y=+/-sqrt(X) ??

    Thank You for the answer, tiny-tim.

    As for the book, I dont wanna name it and make the otherwise excellent textbook look bad.
     
  5. Ray Vickson

    Ray Vickson 5,878
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    Re: Y=X^1/2 is the same as Y=+/-sqrt(X) ??

    Actually, you would be doing the author a favor by telling us the name and author of the book; that way, professionals could write to him/her about the error, so it could be fixed in subsequent editions.

    RGV
     
  6. SammyS

    SammyS 7,928
    Staff Emeritus
    Science Advisor
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    Gold Member

    Re: Y=X^1/2 is the same as Y=+/-sqrt(X) ??

    On the other hand, if the author is explaining how to solve y2 = x, for y, or solve y2 = 100 for y, then the answers are:
    y = ± √(x) = ±(x)1/2 for y2 = x

    y = ±10 for y2 = 100​
    If this is the case you have only told us part of what the textbook was claiming, although the author may have also left a few details out of her/his explanation.
     
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