Question

The ninth term is 6.Find the sum of the first 17th terms.

Answer 1

Answer:

t9 = 6.......given

so, a + (9-1) d = 6

a + 8d = 6.........1

Sn = n/2 [2a + ( n-1 )d]

S17= 17/2 [2a + (17-1)d]

= 17/2 [2a + 16d]

= 17/2 × 2(a + 8d)

= 17× 6.......from 1

S17= 102