Question

Find S or the sum for the given arithmetic series. a1 = –84, d = –2, n = 22

Answer 1

S₂₂ = - 2310

Explanation:

the sum to n terms of an arithmetic series is

`S_(n)` =
`(n)/(2)` [ 2a₁ + (n - 1)d ]

given a₁ = - 84, d = - 2, n = 22 , then

S₂₂ =
`(22)/(2)` [ (2 × - 84) + (21 × - 2) ]

= 11 (- 168 - 42)

= 11 × - 210

= - 2310

Answer 2

consider the other one I used the wrong method.