Question

e^(2 x)-3 e^x-4=0

Answer 1

sign e^x =t
than will get

t^2 -3t -4=0

(t-4)(t+1)=0
t-4=0
t=4

t+1=0
t=-1

e^x =4
lne^x =lne^4
xlne=4lne
x=4

e^x =-1 not is possibile