Write explicitly function of y defined by the following equation.
$e^y-e^{-y}=2x$
Answer & explanation
Correct answer: option 3
$e^y-e^{-y}=2x$
$⇒e^{2y}-2xe^y-1=0$ (Multiplying by $e^y$)
$⇒e^y=\frac{2x±\sqrt{4x^2+4}}{2}=x±\sqrt{x^2+1}$
$⇒e^y=x+\sqrt{x^2+1}$ (as $\sqrt{x^2+1}>x$, then $x-\sqrt{x^2+1}<0$, which is not possible)
$⇒y=\log_e(x+\sqrt{x^2+1})$