 Hello and welcome to the session. I am Deepika here. Let's discuss the question whether the following form an AP, if they form an AP, find the common difference D and write three more terms 1, 3, 9, 27 and so on. Let's start the solution. Our given list of numbers is 1, 3, 9, 27 and so on. We have a2-a1 is equal to 3-1 which is equal to 2 and a3-a2 is equal to 9-3 which is equal to 6. Since a2-a1 is not equal to a3-a2 therefore the given list of numbers does not form an AP. The answer for this question is that 1, 3, 9, 27 do not form an AP. Let us know. Is the answer for this question? I hope it is clear to you. Bye and have a good day.