Given a geometric sequence 160, 80, 40, 20, ... 1) Find

Kaycee Roche

Kaycee Roche

Answered question

2021-08-11

Given a geometric sequence 160, 80, 40, 20, ...
1) Find the 8th term of the sequence (in decimal form)
2) Find the sum of the first 8 terms of the sequence

Answer & Explanation

hosentak

hosentak

Skilled2021-08-12Added 100 answers

1) The formula for the nth term:
an=a1rn1
From the given:
a1=160
r=80160=0.5
n=8
Substitute
a8=160(0.5)81
=160(0.5)7
=1.25
2) The formula for the sum of the first nn terms:
Sn=a1(1rn)1r
Substitute:
S8=160(10.58)10.5
=160(0.99609375)0.5
=318.75

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