I need to find the Sn for the arithmetic series with d = -4, an = 27, and n = 9

Khalfanebw

Khalfanebw

Answered question

2022-09-23

I need to find the Sn for the arithmetic series with d = -4, an = 27, and n = 9

Answer & Explanation

anekesanxl

anekesanxl

Beginner2022-09-24Added 12 answers

We may use the formula for the sum to n terms of an arithmetic series :
k = 1 n [ a + ( k - 1 ) d ] = n 2 [ 2 a + ( n - 1 ) d ]
= 9 2 [ ( 2 ) ( 27 ) + ( 9 - 1 ) ( - 4 ) ]
= 99

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