SOLUTION: If 2;x;18;... Are the first three terms of a geometric sequence determine the value(s) of x

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Question 1020960: If 2;x;18;... Are the first three terms of a geometric sequence determine the value(s) of x
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
if 2,x, and 18 are in geometric progression, then x%2F2+=+18%2Fx
==> x%5E2+=+36 ==>x = 6 or -6.
Therefore there are two possibilities, either x = 6 (when the common ratio is 3), or x = -6 (when the common ratio is -3).