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Determine whether the equation represents y as a function of x

by Psichlohomeo
Tags: determine, equation, function, represents
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Psichlohomeo
#1
Oct7-09, 10:56 PM
P: 7
1. X^2 + y = 8



2. Relevant equations



3. my steps:
y = 8 - x^2
x^2 = 8 - y

(8-y) + y = 8

Not a function.
My logic is, because the equation does not equal y, it is not a function


Please show me step by step the right answer, and preferably the reason why.
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Dick
#2
Oct7-09, 11:12 PM
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You already had it in the first step. And it just gets crazy after that. If you don't know why, I think you should look up the definition of 'function' and tell us what it is.
Psichlohomeo
#3
Oct7-09, 11:20 PM
P: 7
Oh. It's not a function because y = -x^2 + 8 ?

Psichlohomeo
#4
Oct7-09, 11:28 PM
P: 7
Determine whether the equation represents y as a function of x

Please assist me in my retardation. :( It is immensely painful.
Dick
#5
Oct7-09, 11:28 PM
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Quote Quote by Psichlohomeo View Post
Oh. It's not a function because y = -x^2 + 8 ?
Exactly wrong. y IS a function of x because y=(-x^2)+8. I'm going to ask you once more to look up the definition of a 'function'. Post it here for further discussion.
Mark44
#6
Oct8-09, 12:26 AM
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Quote Quote by Psichlohomeo View Post
3. my steps:
y = 8 - x^2
x^2 = 8 - y
The two equations above are equivalent to the one you started with, but as Dick already said, you had what you need in the first one above, and the one after that is just wasted motion.
Quote Quote by Psichlohomeo View Post
(8-y) + y = 8
Now this one is always true, but is completely unrelated to the equation you started with and the two above.


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