Useful property: 1/(a/b) = b/aADILSAFDER wrote:Q: If f(x)= 1/(1+x), then find the value of f[f{f(x)}],at x=5:
A. 21/27
B. 21/39
C. 15/39
D. 15/27
E. None
We want: f[f{f(5)}]
f(5) = 1/(1 + 5) = 1/6
So, f[f{f(5)}] = f[f{1/6}]
f{1/6} = 1/(1 + 1/6) = 1/(7/6) = 6/7
So, f[f{1/6}] = f[6/7]
Finally, f[6/7] = 1/(1 + 6/7) = 1/(13/7) = 7/13
Answer: B (since 21/39 reduces to the equivalent fraction 7/13)
Cheers,
Brent