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Kato
Registered User

Ok...the only reason I am asking this is because I had to copy the problems from a friend's book because my book should show up sometime next week. Otherwise, I would look through the book to find my answer. Here is the problem:

Find the domain of the function:

I don't want anyone to do the problem for me. I just need a little guidance. The domain is basically the x axis. So...is the domain the result of the numerator combined with the result of the denominator? As in...this is a Piece Wise?

P.S. Sorry if that is not coming out right...I don't know how to make the x to the second power show up properly with BBCode. The 5x + 4 is the numerator, rest is the denominator in case it didn't come out right.

Find the domain of the function:

```
5x + 4 / x(squared) + 3x + 2
```

I don't want anyone to do the problem for me. I just need a little guidance. The domain is basically the x axis. So...is the domain the result of the numerator combined with the result of the denominator? As in...this is a Piece Wise?

P.S. Sorry if that is not coming out right...I don't know how to make the x to the second power show up properly with BBCode. The 5x + 4 is the numerator, rest is the denominator in case it didn't come out right.

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## Posts

http://www.freemathhelp.com/domain-range.html

for example if the equasion was 2/x x cannot be 0 as then you would be dividing by zero.

DraygoonYou know a fraction can't have a denominator of zero, right? Hopefully that's a good starting point.

You mean the domain is all real numbers. The x-axis is just one piece of a co-ordinate system, and it could be anything depending on what "variables" we are working with.

Not quite; the domain of the rational function is the intersection of the domain of the numerator and the domain of the denominator. In this case you're going to get all reals, since both the num and dom are polynomial functions. Now you need to find which real numbers will make the entire function undefined, and that occurs when you have a zero in the denominator.

The more of these you do you'll start just looking at a function and recognizing where things will go wrong.

Or to put it another way; they're asking "what are all of the possible numbers that you can put into the expression and get a real number back?"

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