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

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

Homework Statement




This is from a textbook:

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

Homework Equations


The Attempt at a Solution



100^1/2=10

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

Thanks.
 

Answers and Replies

  • #2
tiny-tim
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hi solve! :wink:
This is from a textbook:

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

Homework Equations


The Attempt at a Solution



100^1/2=10

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

Thanks.

you're right, it's wrong! :smile:

(which book?)
 
  • #3
solve
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hi solve! :wink:


you're right, it's wrong! :smile:

(which book?)

Thank You for the answer, tiny-tim.

As for the book, I dont wanna name it and make the otherwise excellent textbook look bad.
 
  • #4
Ray Vickson
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Thank You for the answer, tiny-tim.

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

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
 
  • #5
SammyS
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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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