FUNCTIONS F3

 If F(x) = 2x + 50; Find F^-1(200)

 

Solution

 

HINT: F^-1(x) means inverse.

 

PROCEDURE:

Make x the subject and then interchange x and y variables.

 

Let y=F(x)

 

So,  y= 2x + 50

 

y – 50 = 2x

 

y – 50  = 2x    dividing by 2 on both sides

   2          2

 

y – 50   = x

   2

 

x  =   y – 50     after rearranging

           2

 

 y^-1 = x – 50     after interchanging x and y variables.

             2

 

F^-1(x) = x – 50     after interchanging x and y variables.

                2

 

Now we find F^-1(200)

 

F^-1(200) = 200– 50     

                     2

 

F^-1(200) = 150     

                   2

 

F^-1(200) = 75   

 

TRY THIS……………………………

 

If F(x) = 2x + 80; Find F^-1(20)