SOLUTION: (e^2x)-(2e^x)-15=0

Question 407756: (e^2x)-(2e^x)-15=0
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
(e^2x)-(2e^x)-15=0
..
(e^2x)-(2e^x)-15=0
let u=e^x
then u^2=e^2x
we then have a quadratic equation
u^2-2u-15=0
(u-5)(u+3)=0
u-5=0
u=5
u+3=0
u=-3
u=e^x=5
xlne=ln5
x=ln5=1.609
..
u=e^x=-3(reject, an exponential function is always>0)
solution: x=1.609

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