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October 7, 2015
Posted by **Elom Charles** on Friday, February 17, 2012 at 10:37am.

- Mathematics -
**Steve**, Friday, February 17, 2012 at 2:18pmar = a+12

r = a/2

a^2/2 = a+12

a^2 - 2a - 24 = 0

(a-6)(a+4)

so, a=6, r=3

or, a=-4, r=-2

6, 18, 54, 162, ...

or

-4, 8, -16, 32, ...