# composition

• Aug 6th 2007, 04:27 PM
aikenfan
composition
find f * g if f(x) = x^2-7 and g(x) = 2x+4
• Aug 6th 2007, 04:28 PM
aikenfan
do i combine the two equations?
• Aug 6th 2007, 04:43 PM
topsquark
Quote:

Originally Posted by aikenfan
find f * g if f(x) = x^2-7 and g(x) = 2x+4

It depends.
$(f * g)(x) = (x^2 - 7)(2x + 4)$
if this is multiplication of functions.

If it is composition of functions:
$(f \circ g)(x) = f(g(x)) = f(2x + 4) = (2x + 4)^2 - 7$

-Dan
• Aug 6th 2007, 04:55 PM
aikenfan
It is this:
(f \circ g)(x) = f(g(x)) = f(2x + 4) = (2x + 4)^2 - 7
but i am a bit confused
• Aug 6th 2007, 05:38 PM
Krizalid
I think aikenfan asked for $(f\circ{g})$

$(f\circ{g})=f(g(x))=(g(x))^2-7=(2x+4)^2-7$

Which is the same result of Dan