Geometric Sequences

[rsgunter21]

A geometric sequence has a1=8 and a7=(1/8) Find a4 and r.

 

[TchrWill]

A geometric sequence has a1=8 and a7=(1/8) Find a4 and r.

Please clarify your problem statement. It is not at all clear what you mean.

 

[galactus]

\(\displaystyle \L\\a_{4}=8r^{3}\)

\(\displaystyle \L\\\frac{1}{8}=8r^{6}\)

You have two equations with two unknowns...Solve.

 

[pka]

For any geometric sequence \(\displaystyle a_n = a_1 r^{n - 1}\).
Therefore, \(\displaystyle a_7 = 8r^6 = 8^{ - 1} \quad \Rightarrow \quad r = 2^{ - 1}\) .

 

[rsgunter21]

A geometric sequence has a1=8 and a7=(1/8) Find a4 and r.

Please clarify your problem statement. It is not at all clear what you mean.

That's all the problem says.

 

[rsgunter21]

I've been looking at this and i'm still not sure how to work this problem.