Confused with domain

  • Thread starter aleferesco
  • Start date
  • #1
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I just have a question which I'm confused about,

this is the same right?

Domain is (-∞,0) U (0,+∞)

and

Domain D: {XER, x ≠ 0}



and this is the same right?

Domain is (-∞,0) U (5,+∞)

and

Domain D: {XER, x ≠ 0, x≠ 5}



Attempt :

I know that U is used to connect functions,

I'm asking this here since I couldn't find notation online
 

Answers and Replies

  • #2
Dick
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U means union. You are right on the first one. Not so good for the second one. D is the set of xER, where x is not an element of [0,5], the closed interval between 0 and 5.
 
  • #3
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(-∞,0) u [0,5] u (5,+∞) ?

do I always have to include for example the [0,5] when function is XER?

thanks
 
  • #4
Dick
Science Advisor
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That's all of the reals. The set you are describing in the second part is the set of all real x (xER) SUCH THAT x<0 OR x>5. It has two pieces. The xER doesn't say you are including all reals, it just says you are considering ONLY reals.
 

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