Homework Help: Algebra help

Posted by Shawn on Sunday, November 30, 2008 at 6:22pm.

Find (fog)(x)and (gof)(x)if f(x)=x-x^2 and g(x)= 2x+3.
Okay so I did the following:
For f(of)g(x), take (2x+3) - (2x+3)^2
(insert g(x) where the "x" is in f(x) )
For g(of)f(x), take 2[x-x^2] +3

The first answer that I get for (2x+3) - (2x+3)^2 is -4x^2-12x-9
The second answer that I get for
2[x-x^2] +3 is 2x-2x^2+3
are these the answers to the problem?

Algebra help - drwls, Sunday, November 30, 2008 at 8:06pm
You did not subtract the terms correctly for f(of)g(x). You only did the (2x+3)^2 calculation.

Your g of f(x) is correct
Algebra help drwls - Shawn, Sunday, November 30, 2008 at 9:09pm
for f of g(x) I have -4x^2-10x-6

Is this right?

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