[tex]f(x)=\dfrac{1}{9}x-2\to y=\dfrac{1}{9}x-2[/tex]
exchange x with y
[tex]x=\dfrac{1}{9}y-2[/tex]
solve for y
[tex]\dfrac{1}{9}y-2=x[/tex] add 2 to both sides
[tex]\dfrac{1}{9}y=x+2[/tex] multiply both sides by 9
[tex]y=9x+18[/tex]
Answer: [tex]f^{-1}(x)=9x+18[/tex]
