Question

If nth term of an A.P. is (2n+1), what is the sum of its first three terms?

Answer 1

Hey here is your answer

Answer 2

We have :-

=> General term = 2n + 1

First term => n = 1 => 2(1) + 1 = 3

Sum of n terms =

$= > \frac{n}{2} (3 + 2n + 1) = n(n + 2)$

Now, sum of first three terms => n = 3

=> n(n + 2) = 3(3 + 2) = 3 × 5 = 15

Hope it'll help you.....