Question

Which term of ap :21,18,15,.....is zero

Answer 1

$\huge\mathbb\red{Solution:-}$

Given that

★ last term = 0

★ first term a = 21

★ common difference d = 18 - 21 = -3

THEN ACCORDING TO THE QUESTION

l = a + (n - 1)d

0 = 21 + (n - 1)(-3)

0 = 21 - 3n + 3

0 = 24 - 3n

3n = 24

n = 24/3

n = 8

Therefore nth term is 8

Step-by-step explanation:

Answer 2

$\huge{\fbox{\fbox{\bigstar{\mathfrak{\pink{SINGLE♡}}}}}}$

♡

$\huge\mathbb\green{Solution :-}$

21 , 18 , 15 ....

let ,

a1 = 21

a2 = 18

a3 = 15

Last term = 0

First term ( a1 ) = 21

Common difference ( d ) = a2 - a1 = 18 - 21 = -3

nth term of A.P :-

a^n = a + ( n - 1 ) d

===> 21 + ( n - 1 ) ( -3 )

===> 21 - 3n + 3

===> 24 - 3n

3n => 24

n => 24/3

n => 8