Question

If the sum of first n terms of an ap is 2n+3n^2 what is its cd

Answer 1

Answer:

By the question,

Sn=

$2n + 3n {}^{2}$

cd=?

We know that ,

$sn = \frac{n}{2} \times (2a + (n - 1) \times cd)$

$2n + 3n {}^{2} = \frac{n(2a + (n - 1) \times cd)}{2}$

4n+6n^2=2an+cd×n^2 - cd×n

Comparing both equations

cd= 2

a = 1