If the sum to n terms of the A.P.-9,-1,7, ... is 2175, find n.

If the sum of n terms of an A.P is S_n=3n^2+5n then find the Common difference:

find the middle term of the A.P 10,7,4, .....,(-62)

If the sum of first nine terms of an A.P is 171 and that of first 24 terms is 996,find the sum of first 41 terms.

If the sum of three consecutive terms of an A.P is 21 and the sum of the squares of the terms is 165,find the terms.

The first, fourth and thirteenth term of an A.P. are in G.P. If the first term of the A.P. is 3, find the A.P.

Find the sum to n term of the G.P 1/2-1/4+1/8-1/16+ …....

Find the number of terms of the A.P. 63,60,57......so that their sum is 693.Explain the double answer.

If the sum of first n,2n,3n terms of an A.P. be S_1 , S_2 and S_3 respectively then prove that S_1+S_3=2S_2

If the sum of first n,2n,3n terms of an A.P. be S_1 , S_2 and S_3 respectively then prove that S_3=3(S_2-S_1)

The sum of n terms of the A.P. sqrt2,sqrt8,sqrt18,sqrt32,…. is a)1/2n(n+1) b)2n(n+1) c)1 d) 1/sqrt2n(n+1)