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# C3; Question on functions Watch

1. f(x) = (x^2 -4)/3

Find f^-1

Is the answer +/- SQRT(3x+4) ?
2. (Original post by MSI_10)
f(x) = (x^2 -4)/3

Find f^-1

Is the answer +/- SQRT(3x+4) ?
Is there a restriction on the domain of f(x)?

Your answer can't be right if you recall what you know about the definition of a function.
3. (Original post by MSI_10)
f(x) = (x^2 -4)/3

Find f^-1

Is the answer +/- SQRT(3x+4) ?
I think you only want because otherwise the inverse won't be a function.
4. (Original post by Mr M)
Is there a restriction on the domain of f(x)?

Your answer can't be right if you recall what you know about the definition of a function.
Ah whoops yeah forgot to include it in Q..

The domain for the original function was less or equal to 0
5. (Original post by MSI_10)
Ah whoops yeah forgot to include it in Q..

The domain for the original function was less or equal to 0
6. (Original post by Mr M)
- SQRT (3x+4) since the range has to be less than or equal to 0 for the inverse function..
7. (Original post by MSI_10)
- SQRT (3x+4) since the range has to be less than or equal to 0 for the inverse function..
That's right.
8. (Original post by Mr M)
That's right.
Thanks, also, would the range for the original function be less or equal to -4/3?

I input x=o as the domain said that is the highest value it could be into f(x) which gives (0^2 - 4) /3

I got my core 3 paper back and apparently my answer is wrong, rather confused tbf..
9. (Original post by MSI_10)
Thanks, also, would the range for the original function be less or equal to -4/3?
No. Can you sketch it?
10. (Original post by Mr M)
No. Can you sketch it?
Nope..

So what's the first step to solving for the range? Thought it was to use the value given in the domain..

EDIT: Wait a sec, is the answer more than or equal to -4/3??
11. (Original post by MSI_10)
Nope..

So what's the first step to solving for the range? Thought it was to use the value given in the domain..

EDIT: Wait a sec, is the answer more than or equal to -4/3??
Yes.

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