 Hi and welcome to the session. Let us discuss the following question. The question says the edit term TN of an AP is given by TN is equal to 5 minus 2n. Find the sum of first 25 terms of the AP. Let's now begin with the solution. We are given that edit term of the AP is 5 minus 2n. Now for determining the sum we have to first find out the first term and the common difference that is T. Now for determining first term we will put it as 1. So T1 is equal to 5 minus 2 that is 3. Now for n is equal to 2, T2 is equal to 5 minus 2 into 2 that is 1. D is equal to T2 minus T1 that is 1 minus 3 that is minus 2. We know that sum of n terms of AP is given by n by 2 into 2a plus n minus 1 into d. We have to find the sum of first 25 terms. So n is equal to 25. And we have already found out that a that is first term is equal to 3 and common difference that is d is equal to minus 2. Now substitute these values in this formula. So s25 is equal to 25 divided by 2 into 2 into 3 plus 25 minus 1 into minus 2. This is equal to 25 by 2 into 6 plus 24 into minus 2. This is equal to 25 by 2 into 6 minus 48 and this is equal to 25 into minus 21 and this is equal to minus 525. Hence our required answer is minus 525. So this completes the session. Bye and take care.