if ƒ is a one to one and ƒ(4)=8,

then ƒ-1(8)= 4 but how do i get the ƒ(4)-1=?

I know

Question

if ƒ is a one to one and ƒ(4)=8, 

then ƒ-1(8)= 4 but how do i get the ƒ(4)-1=?

I know

mathmale · Answer

If f(x) is one-to-one, the implication is that f(x) has an inverse function, which we denote by $$f ^{-1}(x)$$

mathmale · Answer

if you are given (x,y)     [ which here are (4,8) }, you can evaluate the inverse function at y very easily:

Starting with f(4)=8,
reverse the order, replacing f with $$f ^{-1}(x)$$   your result should be $$f ^{-1}(8)=4$$

mathmale · Answer

It's really that simple.  But you must understand the relationship between f(x) and its inverse $$f ^{-1}(x)$$

mathmale · Answer

and know how to find the inverse function from f(x).