If the n^th</

Given A.P. Series: –1, 4, 9, 14, ......

Since the series is an A.P. series hence between every consecutive terms there is a common difference (d)

We know that the n^th term in an A.P. series is given by

t_n = a + (n–1)d

where

t_n : Represents the n^th term of an A.P.

a : Represents the first term of the A.P. series

d : Represents the common difference

n : Represents the position of n^th term of the A.P.

So according to the problem:

129 = -1 + (n-1) × 5

⇒ 130 = (n-1) × 5

⇒ n-1 = 26

Answer: The value of n = 27