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Precalculus 0704213.pdf - Exercises 1.1.4, Question 10

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Precalculus 0704213.pdf - Exercises 1.1.4, Question 10

John
Hi guys,

Firstly, thank you so much for the open textbooks.  I'm using the Precalculus one as suggested by Coursera.  I'm enjoying it so far, but I do have a question regarding the aforementioned exercise.

The book states (bottom of p.14):

"In Exercises 8 - 19, write the set using interval notation."

The particular set in question is as follows: { x | x != -3, 4 }

The answer is given as: (-infinity, -3) U (-3, 4) U (4, infinity)

I understand why the answer is what it is, but I wonder if the actual set definition should be: { x | x != 3, x != 4 }.  Having looked around at other examples online (e.g. http://www.mathsisfun.com/sets/set-builder-notation.html - scroll all the way to the bottom), each condition seems to be listed explicitly.  I misunderstood the comma here, and thought the set was all x such that x is not equal to -3, and 4 is an element of the set.  

Is it typical to condense conditions using commas like this, or is this a minor correction that should be made?

Kind regards,

John
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Re: Precalculus 0704213.pdf - Exercises 1.1.4, Question 10

Carl Stitz
Administrator
I'll bring this to Jeff's attention.

Thanks,

Carl
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