• Mar 18th 2013, 10:38 AM
swishh
Hello all, I need the answer to the following equation, I'd very much appreciate it!

find A)f o g and b) g o f given F(x) = square root of (x+4) and g(x) = x^2 - 4

if you could give me the answer and briefly go over the steps in finding the equation, i'd be glad! (Talking)
• Mar 18th 2013, 11:13 AM
MINOANMAN
Swishh

do you understand what fog and gof means....it is easy...just replace in the place of x the other function
ie. gof(x): get g(x) as function and instead of x replace (substitute) the whole f(x) as it is......same for fog revise the chaper of the composite functions pls.

MINOAS
• Mar 18th 2013, 11:21 AM
HallsofIvy
If, for example, $\displaystyle f(x)= 3x^2- x+ 6$ and $\displaystyle g(x)= x^3+ 2x$ then fog(x)= f(x^3+ 2x)= 3(x^3+ 2x)^2- (x^3+ 2x)+ 6[/tex] and $\displaystyle gof(x)= g(3x^2- x+ 6)= (3x^2- x+ 6)^3+ 2(3x^2- x+ 6)$.
• Mar 20th 2013, 10:13 AM
swishh
bump. are both f o g and g o f = to x?
• Mar 20th 2013, 10:58 AM
Plato
Quote:

Originally Posted by swishh
are both f o g and g o f = to x?

You must realize that $\displaystyle \sqrt{x^2}=|x|\ne x~.$
• Mar 20th 2013, 11:16 AM
swishh
Quote:

Originally Posted by Plato
You must realize that $\displaystyle \sqrt{x^2}=|x|\ne x~.$

is this for f o g or g o f?

is the answer for f o g and g o f both x, or is it absolute value of x?
• Mar 20th 2013, 11:29 AM
Plato
$\displaystyle f(g(-3))=~?~~\&~~g(f(-3))=~?$