## Help me with Pre-Calc.

Post any maths and/or physics related questions here.

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go home wrote:That is obviously Dave Sinkula so go back to http://cboard.cprogramming.com/index.php? and stay there.
Last edited by Guest on Thu Jan 06, 2005 12:21 am, edited 1 time in total.
Guest

Thanks for the link. The first persons post in the left link is pretty much what I am trying to ask. Il use this when I study tonight. My test is tomorro. So wish me luck after I study.

I think through after school lessons, this forum , the internet lessons, and my text book; I can safely say that I might be able to learn how to do this.

~Thanks everyone~
Sin

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Joined: Tue Oct 07, 2003 10:16 am

Simply put: The domain of x is all reals unless there is a value(s) that make x undefined, or where there are no x values.

Take this set:

f(x)={ 2x, x<4}
{ 3x, x>4}

Notice that there is no value at x=4!! So the domain of x is:
{x|x R, x!=4} or all reals except at x=4.

Range works the same way: If there are undefined values, then the range is affected. Otherwise, it is all real numbers as well.
"Given enough time, man can do anything with a bit of string and some Tinker toys." Bruce Bolden, Senior Instructor at the University of Idaho.

leas5040

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Location: Moscow, ID

leas5040 wrote:Range works the same way: If there are undefined values, then the range is affected. Otherwise, it is all real numbers as well.

Hummm... nope! Range is more complicated. The range of f(x)=x^2 is not all reals.

Alvaro
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### Well........

Alvaro wrote:
leas5040 wrote:Range works the same way: If there are undefined values, then the range is affected. Otherwise, it is all real numbers as well.

Hummm... nope! Range is more complicated. The range of f(x)=x^2 is not all reals.

The range is easily found with the caculator for x^2.

Oh and by the way I was able to study enough to understand how to find the domain and range.

for this:
f(x)= {2x, X < 2}
{3x, X >= 2}

The domain would be all reals.
Its almost like common sense when finding the domain for that one. The calculator can also aid to find the domain.

f(x)= 1/(X+2)(X-1)
the domain would be every real number but not equal to -2 and 1.
Easy.

and for F(x)= 1/Square root of (x+1)
The domain would be X >= -1.
Thanks everyone for the help........
Sin

Posts: 1570
Joined: Tue Oct 07, 2003 10:16 am

### Re: Well........

Christopher wrote:The range is easily found with the caculator for x^2.

How would you do that with a calculator?

f(x)= 1/(X+2)(X-1)
the domain would be every real number but not equal to -2 and 1.
Easy.

Yes, except you are missing some parenthesis in that expression. It should be 1/((X+2)(X-1)).

and for F(x)= 1/Square root of (x+1)
The domain would be X >= -1.

Here you got the `X' and `x' mixed up (Math, like C++, is usually case-sensitive), and x=-1 is not in the domain.

Alvaro
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Location: NY, USA

Hummm... nope! Range is more complicated. The range of f(x)=x^2 is not all reals.

Sure, because y<0 is undefined or isn't on the interval. So the range is [0, infinity) or non-negative numbers.
"Given enough time, man can do anything with a bit of string and some Tinker toys." Bruce Bolden, Senior Instructor at the University of Idaho.

leas5040

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Joined: Mon Apr 12, 2004 9:51 pm
Location: Moscow, ID

### Re: Well........

Here you got the `X' and `x' mixed up (Math, like C++, is usually case-sensitive), and x=-1 is not in the domain.

x >= -1 is not in the domain?
Sin

Posts: 1570
Joined: Tue Oct 07, 2003 10:16 am

It should be all reals except x=-1, because that makes the denominator sqrt(0), which is anti-good.
"Given enough time, man can do anything with a bit of string and some Tinker toys." Bruce Bolden, Senior Instructor at the University of Idaho.

leas5040

Posts: 1214
Joined: Mon Apr 12, 2004 9:51 pm
Location: Moscow, ID

### Re: Well........

Christopher wrote:
Here you got the `X' and `x' mixed up (Math, like C++, is usually case-sensitive), and x=-1 is not in the domain.

x >= -1 is not in the domain?

That's not what I said. I said that x=1 is not in the domain. The domain is {x>1}.

Alvaro
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