# f(x) g(x) help

• May 20th 2008, 03:10 PM
Alan
f(x) g(x) help
Question
If f(x) = 4x - 12, and g(x) = x^2 + 12, what is f(g(x))?

Work Done
4(x^2 + 12) - 12
4x^2 + 48 - 12
4x^2 + 36

Is this coorect? I substituted g(x) in the f(x) equation when there was an x.
• May 20th 2008, 03:15 PM
bobak
Quote:

Originally Posted by Alan
Question
If f(x) = 4x - 12, and g(x) = x^2 + 12, what is f(g(x))?

Work Done
4(x^2 + 12) - 12
4x^2 + 48 - 12
4x^2 + 36

Is this coorect? I substituted g(x) in the f(x) equation when there was an x.

That's perfect, Well done.

Here is a harder question for you to try.

$f(x) = \frac{x+3}{x-4}$ and $g(x) = \frac{x-1}{x+2}$

show that $g(f(x)) = \frac{7}{3x-5}$

Bobak
• May 20th 2008, 03:35 PM
Alan
Thanks, I'll probably have some more questions soon. I am reviewing for an exam.