Find the solution of the differential equation \(\left(e^{y-x}\right) d y=\left(e^x-e^y\right) d x\)

Find the solution of the differential equation \(\left(e^{y-x}\right) d y=\left(e^x-e^y\right) d x\)
  1. \(e^y e^x=e^{2 x}-e^{x^2}+c\)
  2. \(e^y e^x=e^x e^{e^x}-e^{e^x}+c\)
  3. \(e^y e^{e^x}=e^x e^{e^x}-e^{e^x}+c\)
  4. \(e^{e^y} e^x=e^x e^{e^x}-e^{e^x}+c\)

Solution

\(\left(e^{y-x}\right) d y=\left(e^x-e^y\right) d x\) \(\begin{aligned} & \Rightarrow \quad e^y \cdot \frac{d y}{d x}=e^{2 x}-e^x \cdot e^y \\ & \Rightarrow \quad e^y \cdot \frac{d y}{d x}+e^x \cdot e^y=e^{2 x} \end{aligned}\) Let \(\quad e^y=z \Rightarrow e^y \cdot \frac{d y}{d x}=\frac{d z}{d x} \Rightarrow \frac{d z}{d x}+e^x \cdot z=e^{2 x}\) \(\text {IF } \quad=e^{\int e^x \cdot d x}=e^{e^x}\) \(\therefore\) Solution is \(Z \cdot e^{e^x}=\int e^{2 x} \cdot e^{e^x} \cdot d x+c\) Let \(\quad e^x=u\) \(\begin{aligned} & & e^x \cdot d x=d u \\ \Rightarrow \quad & Z \cdot e^{e^x} & =\int u \cdot e^u d u+c=u e^u-e^u+c \\ \Rightarrow \quad & e^y \cdot e^{e^x} & =e^{e^x}\left(e^x-1\right)+c \end{aligned}\)

Asked in: AP EAMCET 2020 (17 Sep Shift 1)

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