SOLUTION: e^4x - 8e^2x - 65 = 0

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Question 518113: e^4x - 8e^2x - 65 = 0
Answer by lwsshak3(11628) About Me  (Show Source):
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e^4x - 8e^2x - 65 = 0
let u=e^2x
u^2=e^4x
u^2-8u-65=0
(u-13)(u+5)=0
u=13
or
u=-5(reject, e^2x>0)
..
for u=13
e^2x=13
2xlne=ln13
lne=1
2x=ln13
x=ln13/2
x=1.2825