f(x) = 2x + 1
To find the inverse of a function you just need to switch the x by y or vice-versa:
-> y = 2x + 1
-> x = 2y + 1
After that you isolate the y again:
-> 2y = x - 1
-> y = (x-1)/2
-> f^-1 (x) = (x-1)/2
Answer:
[tex]f^{ - 1} (x) = (x - 1) \div 2[/tex]