Question

2) Which term of the AP 21, 18, 15
, is zero?​

Answer 1

AP:    21, 18, 15, .........

$a=21\\d=18-21=-3\\a_n=0\\n=?\\a_n=a+(n-1)d\\0=21+(n-1)-3\\-21=(n-1)-3\\(n-1)=7\\n=8$

Hence, $8^t^h$ term of the AP is 0.

Answer 2

Answer:

8th term

Step-by-step explanation:

Ap =21, 18, 15....

a=21

d=18-21=-3

an=0

as we know

an=a+(n-1)d

0=21+(n-1)-3

-21=-3n+3

-21-3=-3n

-24=-3n

n=8

so the 8th tern will be 0