 Hello and welcome to the session, let's work out the following problem. It says find the sum of the first 25 terms of an AP whose nth term is given by Tn is equal to 7 minus 3n. So let's now move on to the solution. We are given that the nth term is given by Tn which is 7 minus 3n. Now from this we can easily find out the first term and the 25th term because this is the general form by which the nth term is given. So we can easily find out T1 by putting n is equal to 1 here. So it is 7 minus 3 into 1 that is 4 and 25 P25 would be 7 minus 3 into 25 and this would be equal to 7 minus 75. So this is equal to minus 68. Now the sum of first n terms denoted by Sn is given by the formula n by 2 that is the number of terms into a1 that is the first term plus an that is nth term. Now here we have to find the sum of first 25 terms. So it is S25 is equal to 25 by 2 into a1. a1 is the first term and an is the 25th term since it is T25. So it is 4 minus 68 which is actually plus minus. So we have 25 by 2 into 4 minus 68. So this is again equal to 25 by 2 into minus 64. Now 2 into 32 is 64. So we have 25 into minus 32 which is equal to minus 800. So the sum of first 25 terms of this AP is equal to minus 800. So this completes the question and the session. Bye for now. Take care. Have a good day.