Question

If the sum of first n terms of an ap is 3n^2-2n find the ap and its 19th term

Answer 1

Answer:

Here you are wanted to write the 90th term. So at first find the sum of first 19th term and 18th term and then 20th term. Now if you subtract the sum of first 18th term form the sum of first 19th term then you will find the 19th term. And in a similar way you can find the 20th term.now subtract 19th term from 20th term and then you will find the common difference. By this you can write the common formula of nth term and can find the first term and AP simultaneously