The domain of [tex]$f(x)$[/tex] is the set of all real values except 7, and the domain of [tex]$g(x)$[/tex] is the set of all real values except -3. Which of the following describes the domain of [tex]$(g \circ f)(x)$[/tex]?

A. All real values except [tex]x \neq -3[/tex] and the [tex]x[/tex] for which [tex]f(x) \neq 7[/tex]

B. All real values except [tex]x \neq -3[/tex] and the [tex]x[/tex] for which [tex]f(x) \neq -3[/tex]

C. All real values except [tex]x \neq 7[/tex] and the [tex]x[/tex] for which [tex]f(x) \neq 7[/tex]

D. All real values except [tex]x \neq 7[/tex] and the [tex]x[/tex] for which [tex]f(x) \neq -3[/tex]



Answer :

To determine the domain of the composite function [tex]\((g \circ f)(x)\)[/tex], we need to consider the domains of both functions [tex]\(f(x)\)[/tex] and [tex]\(g(x)\)[/tex].

Here's a detailed, step-by-step solution:

1. Domain of [tex]\(f(x)\)[/tex]: The domain of [tex]\(f(x)\)[/tex] is all real values except 7. Therefore, we can write:
[tex]\[ D_f = \{ x \in \mathbb{R} \mid x \neq 7 \} \][/tex]

2. Domain of [tex]\(g(x)\)[/tex]: The domain of [tex]\(g(x)\)[/tex] is all real values except -3. Therefore, we can write:
[tex]\[ D_g = \{ y \in \mathbb{R} \mid y \neq -3 \} \][/tex]

3. Composite function [tex]\((g \circ f)(x)\)[/tex]: For the composite function [tex]\((g \circ f)(x)\)[/tex] to be defined at a specific value [tex]\(x\)[/tex], two conditions must be met:
- [tex]\(x\)[/tex] must be in the domain of [tex]\(f\)[/tex]. From step 1, [tex]\(x \neq 7\)[/tex].
- [tex]\(f(x)\)[/tex] must be in the domain of [tex]\(g\)[/tex]. From step 2, [tex]\(f(x) \neq -3\)[/tex].

4. Combining the Conditions:
- [tex]\(x\)[/tex] must not be 7 because [tex]\(x = 7\)[/tex] is not in the domain of [tex]\(f\)[/tex].
- [tex]\(f(x) \neq -3\)[/tex] because [tex]\(f(x) = -3\)[/tex] is not in the domain of [tex]\(g\)[/tex].

Putting these conditions together, the domain of the composite function [tex]\((g \circ f)(x)\)[/tex] can be described as the set of all real values [tex]\(x\)[/tex] such that:
- [tex]\(x \neq 7\)[/tex]
- The value [tex]\(f(x) \neq -3\)[/tex]

Therefore, the domain of [tex]\((g \circ f)(x)\)[/tex] is:
[tex]\[ \text{All real values except } x \neq 7 \text{ and the } x \text{ for which } f(x) \neq -3 \][/tex]

Hence, the correct option is:
- All real values except [tex]\( x \neq 7 \)[/tex] and the [tex]\( x \)[/tex] for which [tex]\( f(x) \neq -3 \)[/tex].