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

Which term of AP : 21, 18, 15, ........ is - 81? Also, is any term 0 ?

1.	Which term of AP : 21, 18, 15, ........ is - 81? Also, is any term 0 ? Give reason for your answer
Answer» -81 is 35th term of AP, and 0 is a term of AP