Answers

2016-07-23T16:55:16+05:30
Given:  (2a + 6 d) * 7/2 = 49
        =>  a + 3d = 7
(2a + 16 d) * 17/2  = 289
        =>   a + 8 d = 17
so 5 d = 10   => d = 2 =>  a = 1
series is :  1, 3, 5, 7, 9, ....so sum of n terms :  [2 a + (n-1) d] n/2 = = n^2 
1 5 1