The general solution of the differential equation $\frac{d y}{d x}=\frac{3 e^{2 x}+3 e^{4 x}}{. e^x+e^{-x}}$…

The general solution of the differential equation $\frac{d y}{d x}=\frac{3 e^{2 x}+3 e^{4 x}}{. e^x+e^{-x}}$ is
  1. $y=\mathrm{e}^{-3 x}+\mathrm{c}$, where c is a constant of integration.
  2. $y=\mathrm{e}^x+\mathrm{c}$, where c is a constant of integration.
  3. $y=\mathrm{e}^{3 x}+\mathrm{c}$, where c is a constant of integration.
  4. $y=\mathrm{e}^{-x}+\mathrm{c}$, where c is a constant of integration.

Solution

$\begin{aligned} & \frac{\mathrm{d} y}{\mathrm{~d} x}=\frac{3 \mathrm{e}^{2 x}+3 \mathrm{e}^{4 x}}{\mathrm{e}^x+\mathrm{e}^{-x}} \\ & \Rightarrow \frac{\mathrm{~d} y}{\mathrm{~d} x}=\frac{3 \mathrm{e}^{2 x}\left(1+\mathrm{e}^{2 x}\right)}{\left(\frac{\mathrm{e}^{2 x}+1}{\mathrm{e}^x}\right)} \\ & \Rightarrow \frac{\mathrm{d} y}{\mathrm{~d} x}=3 \mathrm{e}^{2 x} \cdot \mathrm{e}^x \\ & \Rightarrow \mathrm{~d} y=3 \mathrm{e}^{3 x} \mathrm{~d} x \end{aligned}$
Integrating on both sides, we get $y=\mathrm{e}^{3 x}+\mathrm{c}$

Asked in: MHT CET 2024 (15 May Shift 2)

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