What is the domain of (f*g) (x)=45x^2+19x-42?
Can someone please help me? I can not, for the life of me, get this. I need it explained to me in a way I won't forget.

- anonymous

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- Haseeb96

What do u think, what would be the domain for this ?

- anonymous

I think it's completely wrong...but I think it is...(.77, infinity) , and (1.2, infinity)

- welshfella

I assume you know what a domain is?

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- anonymous

But like I said...I'm pretty sure it is completely wrong...

- anonymous

Yes...domain is the X value and it goes from left to right

- welshfella

right This function is a parabola which opens upwards
and looks a bit like
|dw:1442166537213:dw|

- welshfella

excuse the rough drawing but it should give you an idea what the domain is.

- anonymous

It's OK. I understand what you were trying to show me. And I know that part. :)

- anonymous

I need to put the domain in a form like this: |dw:1442166761514:dw| but I don't know how to...

- welshfella

well the domain is all real numbers and you can write it as
(-infinity, + infinity)

- anonymous

Really? I don't need to include any numbers? Wow...I was wrong

- welshfella

no its all reals
think about it you can any number you like into the function and it will give you a value

- welshfella

-10,000,000 , 0 or 555,000,000,000

- anonymous

Oh...ok. That makes since.

- welshfella

yw

- anonymous

:)

- amistre64

the domain depends on the domains of f and g seperately, not combined.

- anonymous

well the original term is f(x)=4x+9 and g(x)=7x-3

- amistre64

spose for instance
f = (x-3)(x-2)(x-1)
g = 1/(x-1)
(f*g) = (x-3)(x-2) .. but the domain is still restricted by g

- amistre64

then there is no issue concerning f*g

- skullpatrol

Use FOIL

- anonymous

45x^2+19x-42?

- skullpatrol

yup :-)

- anonymous

ok.

- amistre64

f can use all real values as inputs
g can use all real values as inputs
so the domain of (f*g) in this case has no restrictions to it ...

- anonymous

Ok...

- skullpatrol

What exactly is the question asking for?

- anonymous

Well I took so long to answer the other question that it gave me another question like it...

- skullpatrol

Is this a program?

- anonymous

Yes...it's mymathlab

- skullpatrol

What grade?

- anonymous

It's college- freshman

- skullpatrol

Post the question please.

- welshfella

oh sorry - i misread the question

- anonymous

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- anonymous

It's ok

- anonymous

Thank you guys/girls!

- skullpatrol

I can barely read that, which part do you need help with?

- anonymous

I got it...thank you guys. Sorry to trouble you guys. :)

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