It is given that if the sum of the first n terms of an Ap is 4n-n2 what is first term? what is the sum of first two terms? what is the second term? similarly find the 3rd and 10th and nth terms.
Sir please give me a detailed solution of this question as it is very important for board examination and it is from ML Aggarwal Avichal Publication Arithmetic Progression Chapter 9 Question no 17
Taking n=1 and we get,
So, the sum of fristr term of an A.P. is 3.
But, sum of first term will be the first term.
So, first term a=3.
Now, taking n=2 and we get,
Then, sum of first 2 terms is 4.
Now, finding Secondterm.
According to given question,
Hence the A.P.is
First term a=3
The third term of
Similarly, 10th term