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If f(x) = ax+b where a and b are real numbers and if f(f(x)) = 9x + 7 then find a+b .

 Dec 13, 2020
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f (f(x) ) =  9x + 7

 

This implies  that   

 

a ( ax + b)  +  b =   9x + 7      simplify

 

(a^2) x  +( ab + b)  =  9x + 7     equate terms

 

a^2  = 9

a  = 3

 

And

ab  + b   = 7

3b + b  =7

4b  =7

b  =7/4

 

a + b =   3 + 7/4 =   19/4

 

 

cool cool cool

 Dec 13, 2020

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