Question

which term of an ap 21 18 15 ........is -18

Answer 1

an=a+(n-1)d
=21+(18-1)-3
=21+17*-3
=21+(-51)
=-30

Answer 2

Answer:

Step-by-step explanation:

Let an = -18

d=18-21=-3

a=21

General formula of A. P

an=a+(n-1) d

-18=21+(n-1) -3

-18-21=(n-1) -3

-39/-3=n-1

12=n-1

n=13

Hence-18 is 13 term of an A. P

Hope it's helpful