Question

If the sum of n terms of an AP is Sn = n2 + 2n + 5 , then nth term of an AP is

Answer 1

Solution:

• Sn = n² + 2n + 5 ... Given

Now, substitute n by n - 1, we get

=> S(n - 1) = (n - 1)² + 2(n - 1) + 5

=> S(n - 1) = n² + 4

We know, tn = Sn - S(n - 1)

=> tn = n² + 2n + 5 - n² - 4

=> tn = 2n + 1

• Therefore, the nth term of an A.P. is 2n + 1.