The graphs of ff and f1f^{-1} are symmetrical about the line y=x.y=x.

Examples

x{x}
y{y}
(0,1){\left(0 , 1 \right)}
(1,8){\left(1 , -8 \right)}
(1,0){\left(1 , 0 \right)}
(8,1){\left(-8 , 1 \right)}
y=f(x){y=f(x)}
y=f1(x){y=f^{-1}(x)}
y=x{y=x}
f:x9x+1for xR,0x<1.{f: x \mapsto - 9 x + 1} \allowbreak \quad \allowbreak {\textrm{for } x \in \mathbb{R}, 0 \leq x < 1.}
f1:x19x+19for xR,8<x1.{f^{-1}: x \mapsto - \frac{1}{9} x + \frac{1}{9}} \allowbreak \quad \allowbreak {\textrm{for } x \in \mathbb{R}, -8<x\leq 1 .}
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