MCQ
Solution of the differential equation $\frac{e^x-e^{-x}}{e^x+e^{-x}}=\frac{d x-d y}{d x+d y}$, is
  • A
    $2 y e^{2 x}=C \cdot e^{2 x}+1$
  • $2 y e^{2 x}=C \cdot e^{2 x}-1$
  • C
    $y e^{2 x}=C \cdot e^{2 x}+2$
  • D
    none of these

Answer

Correct option: B.
$2 y e^{2 x}=C \cdot e^{2 x}-1$
Given equation $\frac{e^x-e^{-x}}{e^x+e^{-x}}=\frac{d x-d y}{d x+d y}$
Applying componendo and dividendo, we get
$\frac{d y}{d x}=\frac{e^{-x}}{e^x}$
$\Rightarrow d y=e^{-2 x} d x$
$\Rightarrow 2 y=-e^{-2 x}+C ($ Integrating both sides $)$
$\Rightarrow 2 y e^{2 x}=C \cdot e^{2 x}-1$

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