I think s = x2-x2x-1
 Shaswata Roy I guess it is wrong. Shaswata Roy I guess it is wrong.
 
Find the summation
s=x+x2+x4+x8.......till infinity

    s=x+x2+x4+x8.......∞
=>s= x(1+x2+x4+x8...∞)
=>s=x(1+s)
=>s=x1-x
 Shaswata Roy Check again.You made a mistake.
Shaswata Roy Check again.You made a mistake. Sayan Sinha In the second step, it should have been s=x(1+x+x^2+x^4...inf)
Sayan Sinha In the second step, it should have been s=x(1+x+x^2+x^4...inf) Shaswata Roy You Sure...It's still wrong.
Shaswata Roy You Sure...It's still wrong. Sayan Sinha I know the it should have been x^3..x^5 and so on. So, how about taking x^2 common?
Sayan Sinha I know the it should have been x^3..x^5 and so on. So, how about taking x^2 common? Sayan Sinha Nope. Doesn't work...
Sayan Sinha Nope. Doesn't work...
IF X<1,
THEN S=1+X;
IF X≥1 ,
THEN S=∞
 Asish Mahapatra A simple check : at x=0, S = 0 :)
Asish Mahapatra A simple check : at x=0, S = 0 :)
IF X<0 ,
THEN S=1-X;
 Himanshu Giria NO SORRY 
IT WILL B 1+X ONLY
Himanshu Giria NO SORRY 
IT WILL B 1+X ONLY
 Sayan Sinha My solution works that way, right??? :)
Sayan Sinha My solution works that way, right??? :) Sayantan Hazra Simple check : At x = -1, acc. to u, S = 0. But is it?
Sayantan Hazra Simple check : At x = -1, acc. to u, S = 0. But is it? 
Hint: Concentrate on 2nd,3rd,4th terms leaving aside the 1st term.... :)

This is a Lacunary function [See-"http://en.wikipedia.org/wiki/Lacunary_function"].
It does not have a closed form.
