Question

find the 21st and 40th term of sequence whose nth term is defined by an= 1 if odd and -1 if even​

Answer 1

Step-by-step explanation:

Let the first term is a and

Let the first term is a and Put value a=−d in equation (2) we get

Let the first term is a and Put value a=−d in equation (2) we get−d+5d=−8

Let the first term is a and Put value a=−d in equation (2) we get−d+5d=−8⇒4d=−8

Let the first term is a and Put value a=−d in equation (2) we get−d+5d=−8⇒4d=−8⇒d=−2