Determine whether the equation represents y as a function of x


by Psichlohomeo
Tags: determine, equation, function, represents
Psichlohomeo
Psichlohomeo is offline
#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.
Phys.Org News Partner Science news on Phys.org
Going nuts? Turkey looks to pistachios to heat new eco-city
Space-tested fluid flow concept advances infectious disease diagnoses
SpaceX launches supplies to space station (Update)
Dick
Dick is online now
#2
Oct7-09, 11:12 PM
Sci Advisor
HW Helper
Thanks
P: 25,170
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
Psichlohomeo is offline
#3
Oct7-09, 11:20 PM
P: 7
Oh. It's not a function because y = -x^2 + 8 ?

Psichlohomeo
Psichlohomeo is offline
#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
Dick is online now
#5
Oct7-09, 11:28 PM
Sci Advisor
HW Helper
Thanks
P: 25,170
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
Mark44 is offline
#6
Oct8-09, 12:26 AM
Mentor
P: 21,009
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.


Register to reply

Related Discussions
determine pdf of function with gamma pdf Calculus & Beyond Homework 0
Determine a function that calculates the nth weight factor of a wave function Advanced Physics Homework 0
Determine the function so that the integral holds Calculus & Beyond Homework 6
How to determine when a function changes sign? General Math 1
Equation that represents the force? Introductory Physics Homework 13