Question

Which term of the AP:21, 18, 15,..... -81? Also, is any term 0? Give reason for the answer.

Answer 1

Answer:

n=8

Step-by-step explanation:

a=21

d=18-21=-3

Let an=0

an=a+(n-1)d

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

-21=-3n+3

-21-3=-3n

-24=-3n

n=24/3

n=8

Since value of 'n' is positive 0 is the 8th term in this AP

Answer 2

Answer:

There are total of 35 terms and 0 is the 8 term

Step-by-step explanation:

we use the general equation $a_{n} = a + (n-1)d$

a = 21

d = -3

$a_{n} = -81$

Using the equation,

-81 =21 +(n-1)-3

-81-21 = (n-1)-3

-102/-3 = (n-1)

34 = n-1

n = 35.

To find if zero is a term, Let $a_{n} = 0$

0 = 21 + (n-1)-3

-21 = (n-1)-3

-21/-3 = n-1

7 = n-1

8 = n

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