Question

The sum of 'n' term of AP is 24,21,18,....is 108. Find 'n'

Answer 1

HERE IS YOUR ANSWER,

Sn=n/2[2a+(n-1)d]

108=n/2[2(24)+(n-1)-3]

108=n/2[48-3n+3]

108=n/2[51-3n]

108×2=n(51-3n)

216=51n-3n^2

51n-3n^2-216 × -

3n^2-51n+216

Factorize this eqn.

After factorization we get the roots 10 and 7

THEREFORE n=10 or 7

HOPE THIS HELP YOU ❤️

PLEASE MARK THIS AS BRAINLIEST ❤️

Answer 2

What's a ?

=> a is the first term of the AP .

What's d ?

=> d is the common difference between the terms.

AP stands for Arithmetic Progressions.

How to write an Arithmetic Progression with the help of first term 'a' and common difference 'd'?

=> Arithmetic Progression -

a , a+d , a+2d , a+3d , a+4d ...

What is an Arithmetic Progression?

A sequence whose terms increase or decrease by fix number is called arithmetic progression.

And this fix number is - 'd' aka common difference between the terms.