Functions

 

 

 

Contents

 

Relations

 

Functions

 

Composite Function

 

Inverse Functions

 

Absolute Valued Functions

 

Quiz 

 

 

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Inverse Functions

If f is a function, it will map a member x of set A onto a unique member y of set B. There is a function g that can make the return journey. But for g to exist, the range of f in B must be the entire set B, otherwise certain members of B would have no image in A under g. Also no member of B must have more than one arrow arriving from A, otherwise there would be more than one path back to A. Thus, for g to exist, it must be be a one-to-one function. When this occurs, we can find g. g is called the inverse function to f and we can write g = f-1.  

Example 1

Find f-1 in similar form for the one-one function, f:x 3x - 2.

f(x) = 3x - 2 

Let y = 3x - 2
x = (y+2)/3
f-1 : x (x + 2)/3

Example 2

The functions f and g are defined by f:x,x1 and g:x2x+1. Express in similar form the function (fg)-1.

Example 3

Two functions f and g are defined by f:x,x-1 and g:xmx + c, where m and c are constants.

(a) Find the expression of f-1.
(b) Given that g-1(3) = f-1(2) and that f-1g(4) = 1, find the value of m and c.
 
 
f-1:x