[" What is the fourth term of an AP of n terms "],[" whome sum is "n(n+1)?]

What is the Fourth term of an AP of n terms whose sum is n (n+1) ?

What is the formula to find the sum of AP to n terms ?

if nth term of an AP is 3n+2 then find the sum n terms.

Find the sum S_n of the cubes of the first n terms of an A.P. and show that the sum of first n terms of the A.P. is a factor of S_n .

If the ratio of sum of m terms of an AP to the sum of n terms of the same AP is (m^(2))/(n^(2)) .Then prove that the ratio of its mth and nth terms is 2m-1:2n-1.

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 an A.P. whose nth terms is t_n=5+6n,n in N.