Exponents and Geometric Sequences

[Louise Johnson]

Hello, Starting a new section and could use some help. Can anyone check this for me?

Question:
The second term of a geometric sequence is 2 and the fifth term is 250. Find the seventh term.


My answer so far..
T2=ar=2 T5 = ar^4=250
ar^4/ar=2/250
R^3 =1/125
R=1/5
A=10
T7=10(1/5)^6=6.4^-4

Thank you
Louise

 

[tkhunny]

Does that make ANY sense to you? Is the sequence increasing or decreasing? If it is INcreasing, r > 1.

Start over where you created the ratio. Something wrong there.

 

[Louise Johnson]

I see your point with the answer clearly needing to be larger as the sequence is increasing.
I had the ratio upside down as well

ar^4/ar=250/2
r^3=125
r=5 (is this both plus or minus five?)

T7=2/5(5)^6=6250

Can anybody let me know if this is correct?

thank you
Louise