To find $(f \circ g)(x)$, also written as $f(g(x))$, you need to substitute $g(x)$ into $f(x)$. Here's the step-by-step process:

1. $f(x) = 2x - 3$
2. $g(x) = 4x$

Now, find $f(g(x))$, which means we will substitute $g(x) = 4x$ into $f(x)$.

$f(g(x)) = f(4x)$

Substitute $4x$ into the expression for $f(x)$:

$f(4x) = 2(4x) - 3 = 8x - 3$

Thus, $(f \circ g)(x) = 8x - 3$.

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Would you like more details on this process, or do you have any other questions?

Here are 5 related questions for further exploration:

1. What is $(g \circ f)(x)$ for the same functions?
2. How do you find the inverse of $f(x)$ and $g(x)$?
3. What is the domain and range of $(f \circ g)(x)$?
4. How do you compose three functions, like $(h \circ g \circ f)(x)$?
5. How does the composition of functions affect their derivatives in calculus?

Tip: Always check the domain of the inner function when performing compositions, as this can affect the domain of the overall composition.