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Algebra
Question

For

$$f ( x ) = \frac { a x + b } { c x + d }$$

find $$f ^ { - 1 } ( x )$$ . If $$c \neq 0$$ , under what conditions on $$a , b , c ,$$ and $$d$$ is $$f = f ^ { - 1 }$$ ?

f$$^{- 1}$$(x) = $$\frac{b - dx}{cx - a}$$