Question

find the sum of first 20 terms of the Ap 9 ,19,29​

Answer 1

Answer:

Exercise. Calculate the sum of the first 20 terms of the arithmetic sequence whose formula for the nth term is: un=1+(n−1)×4. ...

Answers Without Working.

Formula 2. Given an arithmetic sequence, we can calculate the sum of its first n terms, Sn, using the formula: Sn=n2(2.

Answer 2

Step-by-step explanation:

sum of n term=n/2(2a+(n-1)d