Finding Domain

wolverine89

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Nov 15, 2006
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Hi I was wondering if someone could help me on how to find domain. I know the domain is what x can not be but what are the steps in finding domain and how is it written. For example if x can not equal -3 or 2 how do i write it in parathensis form(negative infinity, positive infinity, in union with) Is there a website or text lesson I can refer to. thanks
 
What do you mean?. The domain is not what it 'can not be'.

More aptly, it's what it can be. Simplistically, the domain is what goes in and the range is what comes out.

i.e., What's the domain of \(\displaystyle \L\\\frac{\sqrt{4+x}}{1-x}\)?.

The domain is \(\displaystyle x\geq{-4}\) and \(\displaystyle x\neq{1}\)

To write this mathematically, \(\displaystyle [-4,1)\cup(1,{\infty})\)

Brackets mean the endpoint is included. Parentheses means it's not included.

See why?. Anything less than -4 results in a negative radicand and 1 results in division by 0. The domain is everything but these. I think you may have been thinking the opposite.
 
wolverine89 said:
Is there a website or text lesson I can refer to.
There are many web sites that cover this topic. To find them, try looking through the first page or two of results provided by a search engine for "domain and range", or related keywords.

Eliz.
 
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