function composition

• Jun 24th 2006, 11:51 PM
kwtolley
algebra and trigonometry with analytic geometry problem
Given f(x)=5x+7 and g(x)=x^2+7, find (g 0 f)(x). I think it is (g 0 f)(x) = (5x)^2+14, gut not sue thanks for any help given.
• Jun 25th 2006, 12:19 AM
CaptainBlack
Quote:

Originally Posted by kwtolley
Given f(x)=5x+7 and g(x)=x^2+7, find (g 0 f)(x). I think it is (g 0 f)(x) = (5x)^2+14, gut not sue thanks for any help given.

$(g \circ f)(x)=g(f(x))=g(5x+7)=(5x+7)^2+7$

RonL
• Jun 25th 2006, 12:40 AM
kwtolley
so 5x^2+7 is the answer. thanks again.
• Jun 25th 2006, 12:45 AM
CaptainBlack
Quote:

Originally Posted by kwtolley
so 5x^2+7 is the answer. thanks again.

No.

$
(g \circ f)(x)=g(f(x))=g(5x+7)=(5x+7)^2+7$
$=25x^2+70x+56
$

RonL
• Jun 25th 2006, 05:51 AM
topsquark
Quote:

Originally Posted by kwtolley
so 5x^2+7 is the answer. thanks again.

kwtolley, just a thought. You seem to know the method to do these problems, but you are consistently getting them wrong due to minor errors. My thought it that you are simply trying to do them too fast. If you are not doing so already I would suggest you write down each step of the problem as you are doing it.

-Dan