having using your mtd, i ended up with 2e^x + 2 e^-x = 3e^y -2e^y.
i tried to let e^x = a and e^y =b and then i got
2a + 2(1/a) = 3( b) - 2(1/b)
solving a as a quadratic eqn, i got a and b to be complex numbers..
which according to my notes, it is wrong as the answer should be real values.
did i do sth wrong?