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

1. Feb 12, 2012

### solve

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. Feb 12, 2012

### tiny-tim

hi solve!
you're right, it's wrong!

(which book?)

3. Feb 12, 2012

### solve

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.

4. Feb 12, 2012

### Ray Vickson

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

5. Feb 12, 2012

### SammyS

Staff Emeritus
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.