Answer: Choice D) x can be anything but 13
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Explanation:
The domain of [tex](f \circ g)(x) = f(g(x))[/tex] is the same as the domain of g(x)
The domain for g(x) is [tex]\{x|x \ne 13\}[/tex] saying we can plug in any number we want as long as it's not 13. This is to avoid dividing by zero. The same domain applies for the composite function because
[tex]f(x) = x+7\\\\\\f(g(x)) = g(x)+7\\\\\\f(g(x)) = \frac{1}{x-13}+7\\\\\\(f \circ g)(x) = \frac{1}{x-13}+7\\\\\\[/tex]
and we can see that we still need to kick out x = 13 from the domain to avoid the division by zero issue.
