Question 18861
f(x)=x/(x+1) 
then 
f(f(x))={{{(x/(x+1))/((x/(x+1))+1)}}}
={{{(x/(x+1))/((x+x+1)/(x+1))}}}
={{{x/(2x+1)}}}..this is what it is ...but if it is to be written as 
?/(x^2+2x+1)or shall we say y/(x^2+x+1)...then we have 

y/(x^2+2x+1)=x/(2x+1)..so 
y=(x^2+2x+1)*x/(2x+1)