sum of n terms

The sum to n terms of the series 11+103+1005+"…." is

If the sum to 2n terms of an Ap 2,5,8,11 , …. is equal to the sum to n terms of an AP 57,59,61,63, …. , then n is equal to

If the sum of m terms of an A.P. is same as the sum of its n terms, then the sum of its (m+n) terms is

If the sum of m terms of an AP is the same as the sum of its n terms , show that the sum of its (m+n) terms is zero .

Find the sum to n terms of the series,whose n^(th) terms is given by : n(n+1)(n+4)

Find the sum to n terms of the series whose n^(th) term is n(n+1)(n+4)

If for every n in N , sum to n terms of an A.P. is 5n^(2)+7n then is 10th term is

Find the sum to n terms of an A.P.whose nth terms is t_(n)=5+6n,n in N

sum on n terms of the series 3,7,11,15,...... is