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 Subject: RE: Need some quick help Author: ycc Date: Jul 31 2004
To answer your question, you need to make clear what is the definition of a
function. To say a function, we have to tell clearly what are the domain and
co-domain. (i.e. the region for the starting value and the region for the
ending value.)
A function means that for any value x in the domain, there is one and only one
value y in the codomain such that f(x)=y.
(Please check your boook if you are still unsure the definition.)
Please see my responses inserted.
On Jul 31 2004, Tryin wrote:
> Hey Folks,

I have just went out and purchased some software to
> help educate myself with Algabra.  However, I do need some quick
> help on the following problems.  If anyone can help me, It would be
> deeply appreciated.  I'm trying to help my kid but I am not doing a
> good job at all.   Thanks

I assume the domain and co-domain are the set of real numbers.

1. Which of the following are
> functions?  Explain your reasoning for a, b, and c.

a. f(x) = 2
> if x>1

f(x) = -1 otherwise

YES. Every x has one and only one corresponding real value.

b. f(x) = 5 if x>0
> f(x) = -5 if x<0

f(x) = 5 or -5 if x = 0

NO. There are two values for f(0), which is not allowed. (Every x should have
only one corresponding value f(x).)

c. f(x) =
> 10/x

NO. f(0)=10/0 is not a real number.  (Every x should have a corresponding value
f(x).)

 Reply to this message Quote this message when replying? yes  no
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