Question

Following are APs or not? If they form an A.P. find the common difference d and write three more terms: 

1, 3, 9, 27 …

Answer 1

1, 3, 9, 27 …

It can be observed that

a₂ − a₁ = 3 − 1 = 2

a₃ − a₂ = 9 − 3 = 6

a₄ − a₃ = 27 − 9 = 18

i.e., a_k+1 − a_k is not the same every time.

Therefore, the given numbers are not in A.P.