If the sum of n terms of an A.P. is 2n2 + 5n, then its nth term is
Here Sn = 2n2 + 5n
Sum of the A.P with 1 term = S1 = 2 + 5 = 7 = first term
Sum of the A.P with 2 terms = 8 + 10 = 18
Sum of the A.P with 3 terms = 18 + 15 = 33
a2 = S2 – S1 = 18 – 7 = 11
d = a2 –a1 = 11 – 7 = 4
nth term = a + (n–1) d
= 7 + (n–1) 4
nth term = 4n + 3