Find left parenthesis f circle g right parenthesis left parenthesis x right parenthesis and its domain when f left parenthesis x right parenthesis equals x squared plus 2 and g left parenthesis x right parenthesis equals start root x plus 5 end root.

(1 point)
Responses

left parenthesis f circle g right parenthesis left parenthesis x right parenthesis equals start root x squared plus 7 end root semicolon left bracket negative 5 comma infinity right parenthesis
Image with alt text: left parenthesis f circle g right parenthesis left parenthesis x right parenthesis equals start root x squared plus 7 end root semicolon left bracket negative 5 comma infinity right parenthesis

left parenthesis f circle g right parenthesis left parenthesis x right parenthesis equals x plus 7 semicolon left bracket negative 5 comma infinity right parenthesis
Image with alt text: left parenthesis f circle g right parenthesis left parenthesis x right parenthesis equals x plus 7 semicolon left bracket negative 5 comma infinity right parenthesis

left parenthesis f circle g right parenthesis left parenthesis x right parenthesis equals x plus 7 semicolon left parenthesis negative infinity comma infinity right parenthesis
Image with alt text: left parenthesis f circle g right parenthesis left parenthesis x right parenthesis equals x plus 7 semicolon left parenthesis negative infinity comma infinity right parenthesis

left parenthesis f circle g right parenthesis left parenthesis x right parenthesis equals start root x squared plus 7 end root semicolon left parenthesis negative infinity comma infinity right parenthesis

1 answer

To find \( (f \circ g)(x) \), we need to evaluate \( f(g(x)) \).

We have the following functions:

  • \( f(x) = x^2 + 2 \)
  • \( g(x) = \sqrt{x + 5} \)

Now, we compute \( (f \circ g)(x) \):

\[ g(x) = \sqrt{x + 5} \]

Substituting \( g(x) \) into \( f(x) \):

\[ f(g(x)) = f(\sqrt{x + 5}) = (\sqrt{x + 5})^2 + 2 \]

Calculating this gives:

\[ (\sqrt{x + 5})^2 = x + 5 \]

Thus, we have:

\[ f(g(x)) = x + 5 + 2 = x + 7 \]

Now we need to determine the domain of \( (f \circ g)(x) \). The domain of \( g(x) \) must be considered first. The function \( g(x) = \sqrt{x + 5} \) is defined when the expression under the square root is non-negative:

\[ x + 5 \geq 0 \quad \Rightarrow \quad x \geq -5 \]

Since \( f(x) \) is a polynomial, it is defined for all real numbers.

Therefore, the domain of \( (f \circ g)(x) \) is determined by the domain of \( g(x) \), which is:

\[ [-5, \infty) \]

Now we can summarize our result:

\[ (f \circ g)(x) = x + 7; \quad \text{domain: } [-5, \infty) \]

Thus, the correct response is:

\( (f \circ g)(x) = x + 7; \quad \text{domain: } [-5, \infty) \)