Question

1.3.5+3.5.7+5.7.9+....n term tk series of addition find

Answer 1

F(k) =15+105+315+-----------+k bcoz if n=k so it's right

Answer 2

it's nth term is (2n-1)(2n+1)(2n+3) .=8n^3+4n^2 -2n-3
so Sn=summation of 8n^3 +4n^2-2n-3