Given f(x) = x² + 3x -3 and g(z) = 2x, find f(g(x)).
Solution
First, we need to decide which function will go inside which. Since
our function reads "f of g of z", we know that we are going to
substitute the function for g(x) into every a spot in the f(x)
function.
f(g(x))=(x
)²+3(x
)-3
Next, perform normal order of operations for each term. (Hint:
(2x)² = (2x)(2x))
f(g(x)) = 4
²+3
2-3
Let's look at how this example would be different if it was
performed in the opposite order. Given f(x) = x² + 3x - 3 and
g(x)=2x, find g(f(x)).
In this case, we'll need to plug the whole function for f(x) into the
input (2) spot in the g(x) function.
g(f(x)) = 4
(x² + 3x - 3)
Then we'll distribute to each term.
g(f(x)) = 4(x²)+2(3x)-3 3
Simplify to get the final answer.