If the sum of first 7 term of an ap is 49 and that of 17 terms is 289 find the sum of first n terms

If the sum of first 7 term of an ap is 49 and that of 17 terms is 289

1.	If the sum of first 7 term of an ap is 49 and that of 17 terms is 289 find the sum of first n terms
Answer» The sum of first n terms is n sq n^2 . n2 is the sum of 1st n terms