Question

the sum of n term of the ap is 2n^2+n then 8th term of the ap is

Answer 1

the 1st term of the AP is 2(1²) + 1 = 3 = a

the sum of two terms of the AP is 2(2²) + 2 =10

the 2nd term of the AP is = sum of 1st two terms - 1st term

= 10 - 3 = 7 = a + d

the common difference of the AP is 7 - 3 = 4 = d

nth term of AP is = a + (n - 1)d

8th term of AP is = 3 + (8 - 1)4 = 31