If the sum of first 8 terms of an AP is 50 and that of 17 terms is 289,find the sum of n terms

If the sum of first 8 terms of an AP is 50 and that of 17 terms is 289

1.	If the sum of first 8 terms of an AP is 50 and that of 17 terms is 289,find the sum of n terms
Answer» In this question , you know that S8 = 8/2 ( 2a + (8-1)d )You will get an equation from this and from S17 as well By combining these two equation by elimination or by any other method you will find d and after that you have to put the value of d in Sn = n/2 ( 2a + (n-1)d ) and at last you will get the answer ( the answer can also be a quadratic equation ) .