PLEAASEE HELP...will medal and fan...Let f(x) = x2 + x + 2 and g(x) = 2x2 + 5. Find f(g(x)).

- anonymous

PLEAASEE HELP...will medal and fan...Let f(x) = x2 + x + 2 and g(x) = 2x2 + 5. Find f(g(x)).

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- schrodinger

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- chrisdbest

Is that \[f(x) = x^2 + x + 2; g(x) = 2x^2 + 5\]

- anonymous

yess

- chrisdbest

So you have to put g(x) in for f(x)

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## More answers

- anonymous

how

- chrisdbest

So that will be \[(2x^2 + 5)^2 + (2x^2 + 5) + 2 \]

- chrisdbest

Because you will be inputting every g(x) value into every x in the f(x) field.

- anonymous

so now do I combine like terms or?

- chrisdbest

So \[(4x^4 + 25) + (2x^2 + 5) + 2\]

- chrisdbest

Yes, you can combine like terms now

- anonymous

why did the 2 stay?

- chrisdbest

The 2 stayed because we were plugging in g(x) terms in for f(x)

- chrisdbest

So your final answer should look like \[4x^4 + 2x^2 +32\]

- chrisdbest

Because the "2" didn't have a variable next to it, we didn't have to mess with it.

- anonymous

ohh I see... thank you so much

- chrisdbest

Does that Help?

- anonymous

yes..but im very bad at it though

- chrisdbest

I feel yah man, I need help in Pre-Calc because there are some parts in Pre-Calc that I go str8 to OS for. Even though I'm taking Pre-Calc online, I'm getting 90% of my answers from OS.

- anonymous

I feel you..wish I could help you too. I am taking algebra online but try this website.. mathway.com

- anonymous

@chrisdbest
\[(2x^2+5)^2 \neq 4x^4+25\]
you have to foil that
\[(2x^2+5)^2 = (2x^2+5)(2x^2+5)\]

- chrisdbest

Lols

- chrisdbest

So \[4x^4 + 10x^2 + 25 ?\] That's what you meant?

- anonymous

so confused

- chrisdbest

Did you get the right answer @ sharlin?

- anonymous

+20x² in the middle

- chrisdbest

@sharlin ?

- chrisdbest

Lols thats what I meant to pput. I'm dyslecix

- chrisdbest

* put; * dyslexic

- anonymous

im not sure because its not multiple choice

- freckles

@peachpi was just talking about how (a+b)^2=a^2+2ab+b^2 instead of a^2+b^2
so changes will need to be made to your previous answer @sharlin

- anonymous

what would the final answer be?

- chrisdbest

\[4x^4 +20x^2 +25\]

- anonymous

Im stil confused on how you got there

- anonymous

He made the substitution and got
\[f(g(x))=(2x^2+5)^2+(2x^2+5)+2\]
which is the same as
\[f(g(x))=(2x^2+5)(2x^2+5)+(2x^2+5)+2\]
He multiplied and then combined like terms

- chrisdbest

Peachpi got this. I feel like he can explain it to you better than I can.

- anonymous

with me so far?

- anonymous

yes

- anonymous

ok. now multiply (2x² +5)(2x² + 5) either using foil or the rule @freckles put up

- anonymous

so I got 4x^2+10x^2+10x^2+25

- anonymous

Should be 4x^4. so that was just the first part of the equation. You need to combine it with the rest and combine like terms
4x^4+10x^2+10x^2+25 + 2x^2+ 5 +2

- anonymous

I get a crazy answer

- chrisdbest

Yo @peachpi Ima give you dat gold medal cuz I think you deserve it, cuz I don't got a lot of time to answer everyone's questions.

- anonymous

@sharlin what did you get?

- anonymous

thx @chrisdbest

- anonymous

4x4+22x2+32..idk

- anonymous

that's right

- anonymous

really..im really not sure

- anonymous

yep. trust your work

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