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 Discussion: All Topics in PreCalculus for Properties of Rational Functions Topic: Need some quick help

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 Subject: RE: Need some quick help Author: DUB Date: Aug 1 2004
Thanks YCC.

Can you help on these two as well?

- Suppose you have a lemonade stand, and when you charge \$1 per cup of lemonade
you sell 60 cups.  But when you raise your price to \$2 you only sell 30 cups.
Write an equation for the number of cups you sell  as a function of the price
you charge.  Denote "C" for number of cups, and "P" for the price you charge.
Assume the function is linear.

- Take a look at the table below and write out an equation for f(x).
x -2 -1 0 1 2
f(x) -5 -2 1 4 7

--------------  Thanks again,

On Jul 31 2004, ycc wrote:
> 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).)

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