Question

If the sum of n terms of an A.P. is 2n² + 5n, then its nth term is
A. 4n – 3
B. 3n – 4
C. 4n + 3
D. 3n + 4

Answer 1

Answer:

think (c) option is correct

Answer 2

C. 4n + 3

Step-by-step explanation:

Given: sum of n terms of an A.P. is 2n² + 5n

Find: nth term

Sn = 2n² + 5n

S1 = 2(1) + 5(1) = 7

S2 = 2(4) + 5(2) = 18

a1 = 7

a2 = 18-7 = 11

d = a2 - a1 = 11-7 = +4

S1 will be a. So we have a = 7 and d = 4

Nth term = an = a +(n-1)d = 7 + (n-1)4 = 7 +4n -4 = 3+4n

Option C is the answer.