 Hi and welcome to the session, I am Deepika here. Let's discuss the question for the following APs write the first term and the common difference. Part 1, 3, 1, minus 1, minus 3 and so on. Part 2, minus 5, minus 1, 3, 7, so on. Part 3, 1 by 3, 5 by 3, 9 by 3, 13 by 3 and so on. Part 4, 0.6, 1.7, 2.8, 3.9 and so on. Let us first understand how to find the common difference of a given AP. Now, for an AP whose terms are a1, a2, a3, so on, an, we have d that is a common difference is equal to ak plus 1 minus ak, where ak plus 1 and ak are the k plus 1th and the kth term respectively. This is a key idea behind our question. We will take the help of this key idea to solve the help of question. So, let's start the solution. Solution, part 1 in part 1 given AP is 3, 1, minus 1, minus 3 and so on. Here first term that is a is equal to 3 and common difference that is d is equal to a2 minus a1 which is equal to 1 minus 3 that is minus 2. Now to obtain d in a given AP we need not find all of a2 minus a1, a3 minus a2 and a4 minus a3. It is enough to find only all of them. Hence the answer for this part is a is equal to 3 and d is equal to minus 2. In part 2 our given AP the first term equal to minus 5 and common difference that is d is equal to minus 1 that is a2 minus a1 which is equal to 4. Hence the answer for this part is a is equal to minus 5 and d is equal to 4. In part 3 our given AP is 1 by 3, 5 by 3, 9 by 3, 13 by 3 and so on. The first term that is a is equal to 1 by 3 is equal to a2 minus a1 which is equal to 5 by 3 minus 1 by 3 and this is equal to 2 by 3. Hence the answer for this part is a is equal to 1 by 3 and d is equal to 2 by 3. Move to the part 4. In part 4 given AP is 0.6, 1.7, 2.8, 3.9 and so on is equal to 0.6 and common difference d is equal to 2 minus a1 that is 1.7 minus 0.6 which is equal to 1.1. Hence the answer for this part is a is equal to 0.6 and d is equal to 1.1. I hope this solution is clear to you. Bye and take care.