Math problem that feels like a hemorrhoid

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LetsGo2DSchool

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Can someone help explain this? I'm usually good with these function problems but this one has caused rectal inflammation.

If G(F(x)) = x^2 - 3 and G(x) = x -3, find F(3)

A. 0
B. 6
C. 9
D. 1
E. -3

Answer is C

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Can someone help explain this? I'm usually good with these function problems but this one has caused rectal inflammation.

If G(F(x)) = x^2 - 3 and G(x) = x -3, find F(3)

A. 0
B. 6
C. 9
D. 1
E. -3

Answer is C


I'll take a crack at it. Since g(x)=X-3 and g(f(x))=x^2-3 then f(x)=x^2 and f(3)=3^2=9
 
Hey

I'm assuming you understand that G(F(x)) represents some function F(x) plugged into G(x)

We must figure out what F(x) is in order that when you plug whatever F(x) is into G(x), it will yield G(F(x)) = x^2 - 3 .
Since G(x) is x-3, and when you plug the unknown function "F(x)" into G(x), you get x^2 - 3, F(x) must be x^2. The only way to arrive at the x^2 - 3 function from just x-3 is to plug x^2 into the x, so F(x) must be x^2.

Then you just plug and chug F(3) = 3^2 = 9

btw...new york....are you taking Romano?
 
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How do you get F(x) to equal x^2?

If g(x)=x-3 abd g(f(x))=x^2-3 then you need to find the function of f(x).

What can you plug into g(x) to make the x=x^2? Well x^2. So that means the if f(x)=x^2 then when you plug in f(x) to g(x) you would get x^2-3.


So think of this g(x)=x-3....what is g(x^2)? And that would be your function for f(x)
 
Got it now. Thanks for the Preparation H!

My exam is in a few weeks. No time for Romeo-ano.
 
Oh I get it now. Thanks for the explanation. LetsGo2DSchool: Basically, you are just substituting x^2 for x in g(x)=x-3.
 
Oh I get it now. Thanks for the explanation. LetsGo2DSchool: Basically, you are just substituting x^2 for x in g(x)=x-3.

Dude, we are in sync. The last two postings by us were both submitted at exactly the same time with basically the same message each time.
 
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