What is the 8th term of the geometric sequence 3, 9, 27,...?

1 Answer
Don't Memorise
May 20, 2015

The geometric sequence given is:
#3 , 9 , 27# ...

When provided with a geometric sequence we must first calculate the common ratio #r#

#r# is obtained by dividing a term by its preceding term
1) #9/3 = 3#
2) #27/9= 3#

for this sequence:

  • common ratio # r = 3#
  • first term # a = 3#
  • #n = 8#

The 8th term can be obtained through formula
# T_n = ar^(n-1) = 3 xx 3^((8-1))#
#= 3 xx 3^7#
#= 3 xx 2187= 6561#

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