Question

Find the sum of first 24 terms of the list of numbers whose nth term is given by a_n = 3 + 2n

Answer 1

As a_n = 3 + 2n,

so, a₁ = 3 + 2 = 5

a₂ = 3 + 2 × 2 = 7

a₃ = 3 + 2 × 3 = 9

List of numbers becomes 5, 7, 9, 11, . . .

Here, 7 – 5 = 9 – 7 = 11 – 9 = 2 and so on.

So, it forms an AP with common difference d = 2.

To find S₂₄, we have n = 24, a = 5, d = 2.

Therefore

So, sum of first 24 terms of the list of numbers is 672.