Question

3. What is the sum of first n terms of the AP a, 3a, 5a.........​

Answer 1

Answer:

Given AP a, 3a, 5a,............

Has first term = a

And

common difference =2a

As we know that sum of n terms of an AP having first term a and common difference d is given by

$S_n = \dfrac{n}{2} (2a + (n - 1)d)$

So, sum of n terms of given AP will be :-

$S_n = \dfrac{n}{2} (2a + (n - 1)2a) \\ = \dfrac{n}{2} \times 2a(1 + n - 1) \\ = an(n) \\ = a {n}^{2}$

sum of first n terms of given AP will be an^2.

Answer 2

Refers to attachment ♡♡~