SOLUTION: Find a formula for the nth term of the geometric sequence. Then find the indicated nth term of the geometric sequence. 17th term: 5, 15, 45,. . . an= a17=

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Question 1178485: Find a formula for the nth term of the geometric sequence. Then find the indicated nth term of the geometric sequence.
17th term: 5, 15, 45,. . .
an=
a17=
Found 3 solutions by josgarithmetic, MathLover1, mananth:
Answer by josgarithmetic(39615) About Me  (Show Source):
You can put this solution on YOUR website!
Observe that the common ratio is 3.
Go from there.

Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
the nth term formula of the geometric sequence:
a%5Bn%5D=a%5B1%5D%2Ar%5E%28n-1%29 where n=1, 2,.......
given:
sequence: 5, 15, 45,. . .
a%5B1%5D=5
a%5B2%5D=15
a%5B3%5D=45
so, you multiply first term by 3 to get second term, and multiply second term by 3 to get third term
so, common ratio is r+=3
your formula is:
a%5Bn%5D=5%2A3%5E%28n-1%29
find:
a%5B17%5D=> means n=17
a%5B17%5D=5%2A3%5E%2817-1%29
a%5B17%5D=5%2A3%5E16
a%5B17%5D=215233605


Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
The n th term of geometric sequence is

an= a1*r^(n-1)
The sequence is 5,15,45
15/5 =3
45/15 =3
Hence r=3
a1=5
a17 = 5*3^16
=215233605