Question 1059229

(f o g)(X)
f(x)=3x^2-8x
g(x)=2x

I know the answer I don't know how understand how.
I got this: 6x^2-16x I know it is not correct.
This is the answer: 12x^2-16x
I do not understand how that is the answer.
<pre>{{{f(x) = 3x^2 - 8x}}}                  g(x) = 2x
{{{highlight_green(matrix(1,9, f(g(x)), "=", f(2x), "=", 3(2x)^2 - 8(2x), "=", 3(4x^2) - 16x, "=", highlight(12x^2 - 16x))))}}}