Question 758391
solve for x 
e^2x - 2e^x - 8 = 0
let u=e^x
u^2=e^2x
u^2-2u-8=0
(u-4)(u+2)=0
u=-2=e^x
e^x=-2 (reject, e^x>0)
or
u=4=e^x
e^x=4
xlne=ln4
x=ln4≈1.3863..