Question

where can we use this formula​

Answer 1

You can use this formula when they say you to find the specific term

(Actually it is a generalised formula)

For example If they said you to find the sum of 10 terms

Then here n = 10

So by substituting the value you will get the sum of 10terms

Note:"Every sequence has its own general term"

Hope you understood clearly

Answer 2

Hello friend

this is your answer

We can use this formula in an ap where the first term is 1 and their common difference is also 1.

Prove 1,2,3,4.....n is an AP then their sum will be

$\frac{n}{2} (2a + (n - 1)d)$

:• now on putting the value of a and d we get S

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

This is your answer .

HOPE THIS HELPS YOU ♥️♥️♥️♥️♥️♥️♥️