$\left(e^{x}+e^{-x}\right) d y-\left(e^{x}-e^{-x}\right) d x=0$
The given differential equation is:
$\left(e^{x}+e^{-x}\right) d y-\left(e^{x}-e^{-x}\right) d x=0$
$\Rightarrow\left(e^{x}+e^{-x}\right) d y=\left(e^{x}-e^{-x}\right) d x$
$\Rightarrow d y=\left[\frac{e^{x}-e^{-x}}{e^{x}+e^{-x}}\right] d x$
Integrating both sides of this equation, we get:
$\int d y=\int\left[\frac{e^{x}-e^{-x}}{e^{x}+e^{-x}}\right] d x+\mathrm{C}$
$\Rightarrow y=\int\left[\frac{e^{x}-e^{-x}}{e^{x}+e^{-x}}\right] d x+\mathrm{C}$ ...(1)
Differentiating both sides with respect to x, we get:
$y=\int \frac{1}{t} d t+\mathrm{C}$
$\Rightarrow y=\log (t)+\mathrm{C}$
$\Rightarrow y=\log \left(e^{x}+e^{-x}\right)+\mathrm{C}$
This is the required general solution of the given differential equation.