Which of the following form of an AP? Justify your answer.
1, 1, 2, 2, 3, 3, …
We have a1 = 1 , a2 = 1, a3 = 2 and a4 = 2
a2 - a1 = 0
a3 - a2 = 1
Clearly, the difference of successive terms is not same, therefore given list of numbers does not form an AP.