domain

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czagara

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Sep 24, 2009
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Can someone please help me figure out how to find the domain of this function? I am not understanding these domain things.

5x-7 over or divided by 8-x
 
The Domain is a set of numbers. Specifically, it is the set of all numbers that we can substitute for x.

Well, with this given algebraic ratio we are free to substitute any number we like for x, with one exception.

What happens if the denominator of a ratio turns out to be zero?

Does that question give you any ideas?
 
Then it would be zero, and I don't believe that counts as a real number


Ok, so lets say that i put in , i would get -2/7

I get that, but what does that make my domain?
 
I believe the online class I am working this problem out on, wants a specific answer and I am not sure what the specific answer would be if you can put any number in, for instance are they looking for something like (ifinity, 1) U (-infinity,1). I am so confused.
 
The denominator is 8 - x.

The denominator cannot be zero.

Ask yourself, "What value of x would cause the denominator to be zero?"

The answer to that question is the single value that x cannot be. All other numbers are okay.
 
Yup. (Well, your result is correct, but your work has some issues.)

If x = -8, then the denominator equals zero, WHICH IS NOT GOOD!

So, the domain is all Real numbers except for -8.
 
is that how you write , because i tried x=-8 and it didn't accept that as the answer
 
To write the set of all Real numbers except -8 (using Interval notation), we write a union of two subsets.

Domain: (-?, -8) U (-8, ?)

I have no idea what format your on-line "teacher" wants inputted.
 
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