In the given problem, the sum of n terms of an A.P. is given by the expression,$S_n = 3n^2 + n$Here, we can find the first term by substituting n = 1 as sum of first term of the A.P. will be the same as the first term. So we get,$S_n = 3n^2 + n$$S_1 = 3(1)^2 + (1)$$= 3 + 1 = 4$Therefore, the first term of this A.P. is a = 4.