Replace x by x/2..... do it for n times... and add them... :)
Jeet Sen Sharma then tend x to infinity, to get a eqation of f(x)
Jeet Sen Sharma actually i am stuck after this.... its coming somthing like, f(x)-f(x/2)= (4x^2)/3 then.... !!!
Sourish Ghosh Jeet, do the same thing after this also, put x = x/2. You'll get f(x) - f(x/4n) = something