SOLUTION: solve for x 3^2x

SOLUTION: solve for x 3^2x - 9(3^-2x) = 8

Question 972361: solve for x
3^2x - 9(3^-2x) = 8
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
solve for x
3^2x - 9(3^-2x) = 8
-----
3^2x - 3^(-2x+2) = 8
3^(4x) - 3^2 = 8*3^(2x)
3^(4x) -8*3^(2x) - 3^2 = 0
Sub u for 3^2x
----
u^2 - 8u - 9 = 0
(u - 9)*(u + 1) = 0
-------------
u = 9 --> x = 1
==================
u = -1 extraneous, ignore
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