Test:80 QNo:8

a) n(n+1)(2n+1)/6
b) n(2n²-1)
c) n²(2n²-1)
d) n²(n+1)(2n+1)/6

should the answer be n²(n+1)(2n+1)/6 ?

Answer given is c)

i m getting n(4n²-1)3

oops yes ryt.... there was a typing error...me too.... edited....

Actually yeah, on solving thats what I'm getting.. But, during the test I didnt solve.. I did it by the method of elimination.. And only option d) is valid to get the desired result.. Like putting values n=1 and n=2.. We can see that only d) holds..

put n = 3 , option d aint valid