Engineering Board Exam Reviewer · Functions: Domain, Composition, and Inverses · hard

A linear function f(x)=ax+b satisfies f(1)=5 and f(f(1))=11. Find f(3).

1. 7
2. 8
3. 9
4. 11

Answer

B. 8

Solution

f(1)=a+b=5 and f(5)=5a+b=11. Subtracting: 4a=6 a= 32, b= 72. Then f(3)= 92+ 72=8.

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