# CAT Practice : Functions

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When will we have an invertible function ?

## Invertible Functions

Q.21: If $f(x) = \frac{(x + 6)}{(x+2)}$. Find the value of x for which f(x) = f-1(x)?
1. -3
2. 2
3. Both A and B
4. None of these

Choice C. Both A and B

## Detailed Solution

f(x) = f-1(x) when f(x) = x
=) $\frac{(x + 6)}{(x+2)}$ = x
=) x + 6 = x2 + 2x
=) x2 + x – 6 = 0
=) (x+3) (x-2) = 0
=) x = -3, 2

Correct Answer: Both A and B

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Functions.