Let a ∈ R {\displaystyle {}a\in \mathbb {R} } be fixed. This real number defines a mapping
For a = 0 {\displaystyle {}a=0} , this is the constant zero mapping. For a ≠ 0 {\displaystyle {}a\neq 0} , we have a bijective mapping, the inverse mappiung is
Here, the inverse mapping has a similar form as the mapping itself.