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

by solve
Tags: or sqrtx, yx1 or 2
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solve
#1
Feb12-12, 04:02 AM
P: 94
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.
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tiny-tim
#2
Feb12-12, 05:12 AM
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hi solve!
Quote Quote by solve View Post
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.
you're right, it's wrong!

(which book?)
solve
#3
Feb12-12, 05:36 AM
P: 94
Quote Quote by tiny-tim View Post
hi solve!


you're right, it's wrong!

(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.

Ray Vickson
#4
Feb12-12, 12:47 PM
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Y=X^1/2 is the same as Y=+/-sqrt(X) ?

Quote Quote by solve View Post
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
SammyS
#5
Feb12-12, 01:17 PM
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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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