To find $d(f(x))$, we need to compute the derivative of $f(x) = x + 5$.

Solution:

1. The function $f(x) = x + 5$ is a simple linear function.
2. The derivative of $f(x)$ with respect to $x$, denoted $f'(x)$ or $d(f(x))$, is obtained by differentiating each term: $f'(x) = \frac{d}{dx}(x) + \frac{d}{dx}(5)$
3. Since the derivative of $x$ is $1$ and the derivative of a constant $5$ is $0$, we get: $f'(x) = 1$

So, $d(f(x)) = 1$.

Would you like details on differentiating $g(x)$ as well, or have any other questions?

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Here are some related questions that explore similar ideas:

1. What is the derivative of $g(x) = x^2 - 3$?
2. How would you find the derivative of a product of $f(x)$ and $g(x)$?
3. What is the second derivative of $f(x) = x + 5$?
4. How do you find the derivative of a composite function like $h(x) = f(g(x))$?
5. If $f(x) = x + 5$ and $g(x) = x^2 - 3$, what is $f'(g(x))$?

Tip: The derivative of a constant is always zero, simplifying calculations for functions involving constants.