Question

Which term of the AP: 21,18,15 is -81, and we have to find n.give reason for ur answer ​

Answer 1

Answer:

n=35

Step-by-step explanation:

First term (a)=21

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

an=-81 (Given in question)

we have the formula

an=a+(n-1)d

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

-81=21-3n+3

-81-21=-3n+3

-102=-3n+3

-102-3=-3n

-3n=-105

n=35

Hence 35th term of the A.P is -81

I hope this answer may help you