If sum of first n terms of an AP is 2n + 4, then the sum of first 4 terms is _____.
if the sum of first n terms of an AP is 2n^2-n+1, then find the tenth term of the AP
Sum of n terms of an ap is 2n+3n2 if first term is taken as same and the difference will be doubled then find the sum of the first n terms of an new ap
If the sum of first m terms of an AP is n and the sum of first n terms is m , then show that sum of first (m+n) term is -(m+n).