q. find the sum of all divisors of 9900.

soln. given at back is like dis:-

9900 = 3^2 . 2^2.5^2.11

therfore sum = (3^0+3^1+3^2)(2^0+..+2^2)(..and similarily other two)

 

now everything had gone above my head...plzzz help..i mean why they hv done like dis...what is the basic idea...there must be sum idea ....and why this expression will evaluate answer??plzz help expertse.g.nadeemoidu,hsbhatta sir?