Question

solve e^x + 8e^-x = 6

Answer 1

Let e^x=a
than the equation will be
a+8/a=6 /*a
a^2+8=6a
a^2-6a+8=0
(a-4)(a-2)=0
a=4 or a=2
so
e^x=4 implies x=ln4
e^x=2 implies x=ln2