Question about Composition Functions

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September 13th 2011, 01:18 PM
GaDoomZ

Question about Composition Functions

Ok i know how to solve compositions when Im provided with x

Here I am dealing with f of g of h

f(x) = 2x-2
g(x) = x^2
h(x) = 9-x

so its f(g(h(x)

But how do i start without an x value?
September 13th 2011, 01:23 PM
Plato

Re: Question about Composition Functions

Quote:

Originally Posted by GaDoomZ

Here I am dealing with f of g of h
f(x) = 2x-2
g(x) = x^2
h(x) = 9-x
so its f(g(h(x))

$f \circ g \circ h(x) = f\left( {g\left( {h(x)} \right)} \right) = 2(9 - x)^2 - 2$
September 13th 2011, 01:34 PM
GaDoomZ

Re: Question about Composition Functions

Oh I see haha, guess that was a stupid mistake on my part. Guess I just had to leave X as X...
September 13th 2011, 01:39 PM
GaDoomZ

Re: Question about Composition Functions

Ok how about
f(x) = √x
g(x) = 7√1-x

I tried √7-x, √x, √7x they were all wrong
September 13th 2011, 01:55 PM
HallsofIvy

Re: Question about Composition Functions

Quote:

Originally Posted by GaDoomZ

Ok how about
f(x) = √x
g(x) = 7√1-x

I tried √7-x, √x, √7x they were all wrong

I don't know what you meant by "tried". Plato told you how to find the compositions.
$f\circ g(x)= f(g(x))= f(7\sqrt{1-x}}= \sqt{7\sqrt{1-x}}$
which could also be written
$\sqrt{7}\sqrt[4]{1- x}$

$g\circ f(x)= g(f(x))= g(\sqrt{x})= 7\sqrt{1- \sqrt{x}}$
September 13th 2011, 02:10 PM
GaDoomZ

Re: Question about Composition Functions

When I submitted both of those, it was marked as wrong...
even after simplfying it down to

√7-x and 7-√x
September 13th 2011, 02:15 PM
Plato

Re: Question about Composition Functions

Quote:

Originally Posted by GaDoomZ

When I submitted both of those, it was marked as wrong...
even after simplfying it down to

√7-x and 7-√x

$\sqrt{7\sqrt{1-x}}$
September 13th 2011, 02:50 PM
GaDoomZ

Re: Question about Composition Functions

Nope, still didn't work... I am out of submissions now :(
September 13th 2011, 04:17 PM
GaDoomZ

Re: Question about Composition Functions

Quote:

Originally Posted by GaDoomZ

Nope, still didn't work... I am out of submissions now :(

I am now stuck on G o G of the same problem

I get 7√1-7√1-x which should just be 7√1-x no?
September 13th 2011, 04:28 PM
Plato

Re: Question about Composition Functions

Quote:

Originally Posted by GaDoomZ

I am now stuck on G o G of the same problem

I get 7√1-7√1-x which should just be 7√1-x no?

I think that there must be a flaw in what program you are using.

If this is indeed correct $g(x)=7\sqrt{1-x}$

then $g\circ g(x)=7\sqrt{1-7\sqrt{1-x}~}$ .

If the program does not take that, then either you are typing the symbols incorrectly or there is a flaw in the program.
September 13th 2011, 05:39 PM
GaDoomZ

Re: Question about Composition Functions

Quote:

Originally Posted by Plato

I think that there must be a flaw in what program you are using.

If this is indeed correct $g(x)=7\sqrt{1-x}$

then $g\circ g(x)=7\sqrt{1-7\sqrt{1-x}~}$ .

If the program does not take that, then either you are typing the symbols incorrectly or there is a flaw in the program.

Nope it is showing up as incorrect still
September 13th 2011, 05:56 PM
Plato

Re: Question about Composition Functions

Quote:

Originally Posted by GaDoomZ

Nope it is showing up as incorrect still

Then that is a totally incompetent program or you do not know how to use it. I suspect that you are not using enough grouping symbols.
Look at my LaTeX code:
7\sqrt{1-7\sqrt{1-x}} this gives $7\sqrt{1-7\sqrt{1-x}}$ .
Note how carefully the various parts are grouped together using grouping symbols.

Does that program allow LaTeX coding?
If so the you can copy and paste from here.

In any case, you need to contact the program administrator to discuss these concerns.
September 13th 2011, 06:30 PM
GaDoomZ

Re: Question about Composition Functions

You are correct plato, I was not inputting the second 7 properly. Thank you again