Question

16.Which term of the AP 21, 18, 15..... is zero?​

Answer 1

$\sf{Answer}$

Step by step explanation:-

Given :-

21 , 18 , 15 ..... are In AP

To find :-

Which term is 0

Solution:-

21, 18 , 15 ....AP

First term = 21

a = 21

Common difference = 18 -21 = -3

15 -18 = -3

So,

d = -3

an = 0

Which term is 0

Formula Required:-

an = a + (n-1) d

Just substuite all values

0 = 21 + (n-1) -3

0 = 21 -3n +3

0 = 24 -3n

24 = 3n

n = 8

So, In AP The term 0 is the 8th term

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Answer 2

Step-by-step explanation:

let nth term is zero

a= 21

d= -3

nth = 0

a+(n-1) *d

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

21+(-3n+3)=0

24-3n=0

-3n= -24

n= 8