# more Composition function

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• Dec 28th 2007, 09:18 AM
johett
more Composition function
Given f(x)= (square root) x+3, g(x)=x^2-9 and h(x)=1/x

Determine a) f o g
b) g o h
c) f o g o h
d) g o f o h
• Dec 28th 2007, 09:39 AM
Plato
Here are two examples. Use them to work your problems.
$h \circ f(x) = \frac{1}{{\sqrt {x + 3} }}\,\& \,f \circ h(x) = \sqrt {\frac{1}{x} + 3}
$
• Dec 28th 2007, 12:24 PM
mathgeek777
Quote:

Originally Posted by johett
Given f(x)= (square root) x+3, g(x)=x^2-9 and h(x)=1/x

Determine a) f o g
b) g o h
c) f o g o h
d) g o f o h

For the first one, you simply plug in the function g for x in function f. B is the same process for different functions.

C is a little trickier. What it is asking you to do is plug in the function h for x in function g. Once you get that, you then plug in function f into all x's in the g o h composite function. Then simplify. D is the same thing, but the functions are being plugged in in a different order.
• Dec 28th 2007, 12:40 PM
Plato
Quote:

Originally Posted by mathgeek777
For the first one, . B is the same process for different functions. you simply plug in the function f for x in function g
C is a little trickier. What it is asking you to do is plug in the function g for x in function h. Once you get that, you then plug in function f into all x's in the g o h composite function. Then simplify. D is the same thing, but the functions are being plugged in in a different order.

mathgeek777 you have it all backwards.
Look at the examples that I gave.
You should know that $f \circ g(x) = f\left( {g(x)} \right)$
• Dec 28th 2007, 01:57 PM
mathgeek777
Quote:

Originally Posted by Plato
mathgeek777 you have it all backwards.
Look at the examples that I gave.
You should know that $f \circ g(x) = f\left( {g(x)} \right)$

I've been off today so please forgive me. Today has not been the greatest day in the world for me. :o

You are right, I'll go fix that right away.
• Dec 28th 2007, 06:08 PM
johett
Can someone post the final answers so when I'm finish, I can check if I did it right. Thank you :)
• Dec 29th 2007, 05:04 AM
Plato
Quote:

Originally Posted by johett
Can someone post the final answers so when I'm finish

Don't beg or bump.
You post your answers and let us check to see that you have done something on your own.
This is a help site not a homework done site.
• Dec 29th 2007, 08:05 AM
topsquark
Quote:

Originally Posted by johett
Can someone post the final answers so when I'm finish, I can check if I did it right. Thank you :)

Why don't you post your solution and we'll be happy to look at it.

-Dan