How do you find the 4th, 5th, 6th, and 7th term of the geometric sequence 7, 21, 63...?

1 Answer
Trevor Ryan.
Feb 18, 2016

The general term of a geometric sequence of common ratio #r# and first term #a# is given by
#T_n=ar^(n-1)#

In this case the first term is #a=7# and since it is a geometric sequence, it has a common ratio
#r=21/7=63/21=3#.

Hence general term #T_n=7*(3)^(n-1)#.

#therefore T_4=7*3^(4-1)=189#

#T_5=7*3^(5-1)=567#

Similarly #T_6=1701 and T_7=5103#

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