SOLUTION: 3.15 For f(x)=9x and g(x)=x+9, find the following functions: A. (fog)(x)= B. (gof)(x)= C. (fog)(3)= D. (gof)(3)=

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Question 1012244: 3.15
For f(x)=9x and g(x)=x+9, find the following functions:
A. (fog)(x)=
B. (gof)(x)=
C. (fog)(3)=
D. (gof)(3)=
Answer by ikleyn(52788)   (Show Source): You can put this solution on YOUR website!
.
For f(x)=9x and g(x)=x+9, find the following functions:
A. (fog)(x)=
B. (gof)(x)=
C. (fog)(3)=
D. (gof)(3)=
------------------------------------------------ 
A. (fog)(x) = 9*(x+9) = 9x + 9.

   How it is obtained?
   Take f(x) = 9x and then substitute g(x) = x+9 instead of x into f(x).

B. (gof)(x) = 9*(x+9) = 9x + 9.

   How it is obtained?
   Take g(x) = x+9 and then substitute f(x) = 9x instead of x into g(x).   

The resulting functions are identical in these cases.
This is OK.

C. and D.  <----->  I will not calculate the values for you.
                    You can do it yourself.
                    Surely, the resulting numbers should be the same for C and D, because 
                      the resulting functions are the same for A and B.

Good luck!


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