Inverse Functions

Example 1.  Find the inverse functions of

y = 7 x – 2

Solution.  First, interchange the variables:

x = 7 y – 2

Then solve the equation for y  to find the inverse function:

y = ( x + 2 ) / 7

Thus,
f – 1( x ) = ( x + 2 ) / 7.
Check-up.

f ( f – 1( x ) ) = f ( ( x + 2) / 7 ) = 7 ( x + 2) / 7  – 2 = ( x + 2 ) – 2 = x,

f – 1 ( f ( x ) ) = f – 1( 7 x – 2 ) =( ( 7 x – 2) + 2 ) / 7 = x.

O.K.

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Example 2.  The figure below illustrates the general property of symmetry of two mutually inverse functions:
The graphs of a function and its inverse are reflections of one another off the mirror line y = x.


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