The image contains a mathematical problem written in Indonesian. It reads:

• "Jika $f(x) = 4x - 3$ dan $g(x) = x + 6$, maka rumus $(f \circ g)(x) = 4x + 21$."

This is asking for the composition of two functions, $f(x)$ and $g(x)$, where:

• $f(x) = 4x - 3$
• $g(x) = x + 6$

To find the composition $(f \circ g)(x)$, we substitute $g(x)$ into $f(x)$:

$(f \circ g)(x) = f(g(x))$

1. Start by substituting $g(x) = x + 6$ into the function $f(x) = 4x - 3$:

$f(g(x)) = 4(g(x)) - 3 = 4(x + 6) - 3$

2. Now, simplify the expression:

$= 4x + 24 - 3 = 4x + 21$

Thus, the correct formula for $(f \circ g)(x)$ is:

$(f \circ g)(x) = 4x + 21$

This matches the given result.

Would you like any further explanation or details?

Here are five related questions to explore further:

1. How do you compute the composition of two functions in general?
2. What is the domain of the composition of two functions?
3. How does the result of $f(g(x))$ change if $g(x)$ is a quadratic function?
4. What happens if you reverse the composition, i.e., calculate $(g \circ f)(x)$?
5. How does composition relate to inverse functions?

Tip: When performing function composition, always substitute the inner function into the outer function carefully, paying attention to signs and parentheses.