Answer :
[tex]f(x)=x^2-1[/tex]
1. First, replace f(x) with y
[tex]y=x^2-1[/tex]2. Replace every x with a y and replace every y with an x.
[tex]x=y^2-1[/tex]3. solve for y:
[tex]\begin{gathered} y^2=x+1 \\ y=\pm\sqrt[]{x+1} \end{gathered}[/tex]4. Replace y with f−1(x):
[tex]f^{-1}(x)=\pm\sqrt[]{x+1}[/tex]