let (1^4+2^4+3^4+....n^4)=f(n).then the sum of

∑(2r-1)^4=?(where r=1.....n)

1. f(2n)-16f(n)
2. f(2n)-f(n)
3. f(2n)-4f(n)
4. noe of these

use the summation terms given in this equation
(1^4+2^4+3^4+....n^4)=f(n)
and the given summation to find can be seen as the sum of odd terms of (2n-1) terms.First try to write f(2n) an dthen take out common of 2⁴ from even terms and you will be left with the summation u have to find.
After a very simple reaarangement you will see that you will get the correct answer as A