[tex]f^{-1}(x)=x-5[/tex]
1) As we want to find the inverse function, we need to follow some steps. The first one is to swap the variables like this:
[tex]\begin{gathered} y=x+5 \\ \\ x=y+5 \\ \\ y+5=x \\ \\ y+5-5=x-5 \\ \\ y=x-5 \\ \\ f^{-1}(x)=x-5 \end{gathered}[/tex]
That is the answer.
