Answer
$4a^2 + 4$
Work Step by Step
For these types of problems where we are given a value to plug into composite functions, we evaluate the inner function first. Then we use the output of the inner function and substitute it where we see $x$ in the outer function. We can write this composite function as $h(g(a))$:
Let's begin by plugging in our value of $a$ into the inner function $g(x)$:
$g(a) = 2(a)$
Multiply to simplify:
$g(a) = 2a$
Now, we will use the output $2a$ to plug in for $x$ in the outer function $h(x)$:
$h(g(a)) = (2a)^2 + 4$
Evaluate exponents:
$h(g(a)) = 4a^2 + 4$
