How to find the reverse function of a function

First you have to give values to the X in the function that want to reverse, 

and after having the values for Y that is the same of F(X)

the values of Y are the values for X' and the values of X are the values for Y'(as the picture)

for the values you can conclude that the inverse of:

f(x)=root( x - 1 )

is:

f(x)=squared(x) + 1

You need do this because don't have a rule to find the reverse that could be for any function and any graphic, the function could be cubic square a root and a straight could be anything.

Rute Bezerra de Menezes Gondim