Question
Quantitative Aptitude Question on Algebra
If f(x)=x-5, and f2(x)=f(f(x)), f3(x)=f(f(f(x))) and so on, then find the value of f8(9).
A
-39
B
-26
C
-36
D
-31
Answer
-31
Explanation
Solution
f(x) =x-5
So, f2 (x)=(x-5)-5=x-10
Similarly, f3 (x)=x-15
So, f8 (x)=x-40
Now, f8 (9)=9-40 =−31
So, the correct option is (D): -31