 Hello, I am welcome to the session. I am Deepika and I am going to help you to solve the following question. The question says, find the sum of first 25 terms of NAP whose nth term is 1 minus 4n. Now we know that the sum of the first n terms of NAP is given by Sn is equal to n over 2 into a plus n where a is the first term of NAP and is the last term of NAP. So this is the key idea behind our question. We will take the help of this key idea to solve the above question. So let's start the solution. Now according to the given question, the nth term of NAP is 1 minus 4n. So we have An is equal to 1 minus 4n. So the first term of NAP is given by that is a is equal to 1 minus 4 into 1 which is equal to 1 minus 4 which is further equal to minus 3. Now we have to find the sum of first 25 terms of NAP. So 25th term is the last term of the given NAP. So a 25 is equal to that is the 25th term of NAP is equal to 1 minus 4 into 25. This is equal to 1 minus 100 which is further equal to minus 99. Now according to our key idea, we have the sum of the first n terms of NAP is given by n is equal to n over 2 into a plus n. Now here we have a is equal to minus 3 a 25 which is the last term of the given NAP is equal to minus 99 and n is equal to 25. So on substituting these values we have s 25 is equal to 25 over 2 into a which is minus 3 plus l which is minus 99 and this is equal to 25 over 2 into minus 102 and this is further equal to minus 1275. Hence the answer for the above question is minus 1275. So this completes our session. I hope the solution is clear to you. Bye and have a nice day.