Question 15 of 25

If [tex][tex]$f(x) = x^2 + 3x + 5$[/tex][/tex], what is [tex][tex]$f(3 + h)$[/tex][/tex]?

A. [tex]h^2 + h + 23[/tex]

B. [tex](3 + h)^2 + 8 + h[/tex]

C. [tex]h^2 + 9h + 23[/tex]

D. [tex]\left(x^2 + 3x + 5\right)(3 + h)[/tex]



Answer :

To find [tex]\( f(3 + h) \)[/tex] for the given function [tex]\( f(x) = x^2 + 3x + 5 \)[/tex], we need to substitute [tex]\( x = 3 + h \)[/tex] into the function.

1. Start with the function definition:
[tex]\[ f(x) = x^2 + 3x + 5 \][/tex]

2. Substitute [tex]\( x = 3 + h \)[/tex] into the function:
[tex]\[ f(3 + h) = (3 + h)^2 + 3(3 + h) + 5 \][/tex]

3. Expand [tex]\( (3 + h)^2 \)[/tex]:
[tex]\[ (3 + h)^2 = 9 + 6h + h^2 \][/tex]

4. Expand [tex]\( 3(3 + h) \)[/tex]:
[tex]\[ 3(3 + h) = 9 + 3h \][/tex]

5. Substitute these expanded terms back into the function:
[tex]\[ f(3 + h) = 9 + 6h + h^2 + 9 + 3h + 5 \][/tex]

6. Combine like terms:
[tex]\[ f(3 + h) = h^2 + 9h + 23 \][/tex]

Therefore, the answer is:
[tex]\[ \boxed{h^2 + 9h + 23} \][/tex]

Thus, the correct option is:
[tex]\[ \text{C}.\ h^2 + 9 h + 23 \][/tex]