Find the sum of the arithmetic sequence having the data given a_1=7, d = - 3, n = 20

figoveck38

figoveck38

Answered question

2022-11-13

Find the sum of the arithmetic sequence having the data given a 1 = 7 , d = - 3, n = 20

Answer & Explanation

Lillianna Salazar

Lillianna Salazar

Beginner2022-11-14Added 22 answers

The formula for the sum of an arithmetic sequence when a 1 , d and n are given is:
S u m = ( n 2 ) [ 2 a + ( n - 1 ) d ]
Data provided is:
a 1 = 7 , d = - 3 , n = 20
Here : a 1 = 7 , d = - 3 and n = 20
= ( 20 2 ) [ 2 . 7 + ( 20 - 1 ) . - 3 ]
= 10 . [ 14 + 19 . ( - 3 ) ]
= 10 . [ 14 - 57 ]
= - 430

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