SOLUTION: If the fifth term of a geometric progression is -2 and the seventh term is -8, what is the first term? thanks

Algebra ->  Permutations -> SOLUTION: If the fifth term of a geometric progression is -2 and the seventh term is -8, what is the first term? thanks       Log On


   

Question 974742: If the fifth term of a geometric progression is -2 and the seventh term is -8, what is the first term? thanks
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
a, ar, ar^2, ar^3, -2, ar^5, -8, ....

-2%2Ar%5E2=-8
r%5E2=4
r=-2 or highlight_green%28r=2%29.

ar%5E4=-2
a=-2%2Fr%5E4
a=-2%2F16
highlight%28a=-1%2F8%29