Question

Which term of an AP 21,18,15 is -87

Answer 1

Step-by-step explanation:

A.P :- 21,18,15

here

d = -3

Let nth term of the ap is -87

so by using formula

an = a+(n-1)d

-87 = 21 +(n-1) -3

(n-1)-3 = -87-21

n-1 = -108/-3

n= 36+1

n= 37

so the -87 is 37th term of the Ap

Answer 2

Answer:

a=21

d=(-3)

therefore,(-87) = 21+(n-1)(-3)

-87= 21-3n+3

-87= 24-3n

-3n= 111

n=37

hence, the term is 37