Which term of the ap:21,18,15 ........is _81 ? Also is any term o give reason

Which term of the ap:21,18,15 ........is _81 ? Also is any term o give

1.	Which term of the ap:21,18,15 ........is _81 ? Also is any term o give reason
Answer» continue from above check ur answer a35=21+34x-3 = 21-102= - 81 , also a8=21-7x3=21-21=0 ok verified let nth term = - 81a=21d= - 3an=a+(n-1)d- 81=21+3-3nn=105/3=3535th term = - 81also 0=21+3-3nn=24/3=88th term = 0