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

[solve]

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.

 

[tiny-tim]

hi solve!

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!

(which book?)

 

[solve]

hi solve!


you're right, it's wrong!

(which book?)

Thank You for the answer, tiny-tim.

As for the book, I don't want to name it and make the otherwise excellent textbook look bad.

 

[Ray Vickson]

Thank You for the answer, tiny-tim.

As for the book, I don't want to 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

 

[SammyS]

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.