Question

Find the sum of the following A.S. series
(1) 1 + 5 + 9 + 13 + ... + 57 Ans= 435
(2) 3 - 2 - 7 - 12- ... - 42 Ans= - 195

Answer 1

Step-by-step explanation:

Find the sum of the first 20 terms of the arithmetic series if a 1 = 5 and a 20 = 62 .

S 20 = 20 ( 5   +   62 ) 2 S 20 = 670

Example 2:

Find the sum of the first 40 terms of the arithmetic sequence

2 , 5 , 8 , 11 , 14 , ⋯

First find the 40 th term:

a 40 = a 1 + ( n − 1 ) d                 = 2 + 39 ( 3 ) = 119

Then find the sum:

S n = n ( a 1 + a n ) 2 S 40 = 40 ( 2   +   119 ) 2 = 2420

Answer 2

Answer:

ans: 2420 is it okay I will be back