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If functions $f$ and $g$ have domains $Df$ and $Dg$ respectively, then the domain of $f / g$ is given by

(A) the union of $Df$ and $Dg$
(B) the intersection of $Df$ and $Dg$
(C) the intersection of $Df$ and $Dg$ without the zeros of function $g$
(D) None of the above

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What have you thought about? Given this is a multiple choice problem, the answer is almost literally staring at you... – Clayton Feb 2 '13 at 6:02
up vote 2 down vote accepted

The domain of any composite functions $$f\pm g,~ fg,~f/g,~g/f$$ can be achived by finding $D(f)\cap D(g)$ except that for the fraction forms we should exclude what @Clayton noted nimbly.

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+1 (I just replaced "expect" with "except" ;-) – amWhy Feb 3 '13 at 0:22

Hint: You can divide by any real number except...

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Nice hint +1$$$$ – Babak S. Feb 2 '13 at 20:05

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