Question

Which term of the AP: 21, 18, 15, . . . is – 93?​

Answer 1

a = 21

d = a2-a1 = 18-21 = -3

an = -93

n =?

an = a+(n-1)d

-93=21+(n-1)-3

-93=21-3n+3

-93=24-3n

-93-24=-3n

-117=-3n

-117/-3 = n

39 = n

- will be cancel