If f:R→R,f(f(x))=(f(x))2 , then fff(x) is not equal to
fx42
(f(x))4
fx22
fx4
Replacing f(x) by x, we have f(x)=x2
Now f(f(x))=fx2=x22=x4⇒f(f(f(x)))=fx4=x42=x8=(f(x))4
now fx22 =x8 and fx4 =x8