Dudiwidj
Dudiwidj Dudiwidj
  • 25-05-2017
  • Mathematics
contestada

For the geometric sequence

-1,-2,-4... find a8

Respuesta :

apologiabiology
apologiabiology apologiabiology
  • 25-05-2017
an=a1(r)^(n-1)
a1=first term
r=common ratio

so
firs term is -1

each is double the prevoius
r=2

an=-1(2)^n-1
8th term
a8=-1(2)^(8-1)
a8=-1(2)^7
a8=-1(128)
a8=-128
the 8th term is -128

Answer Link
choco4
choco4 choco4
  • 25-05-2017
Geometric sequence formula gn = g1 (r)^n - 1

To find the ratio you divide g2 by g1

G1 = first number in the series



To find g8 you just plug 8 instead of n

g8 = g1 (r)^8 - 1

g8 = -1 (2)^8 - 1

g8 = -128
Answer Link

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