Chapter 7 - Functions and Graphs - 7.2 Domain and Range - 7.2 Exercise Set - Page 459: 61

The domain of a real function ( a function defined on real numbers) is the set of numbers for which f(x) is defined. $ f(x)=\displaystyle \frac{x+2}{2 }\quad$ can be calculated for any real number, so its domain is $\mathbb{R}.$ $g(x) =\displaystyle \frac{2}{x+3} $can be calculated for any real number, except the ones yielding a zero in the denominator. g is not defined for $x=-3.$ So the domain of g is not $\mathbb{R}$.

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