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If xy=e(x−y)xy = e^{(x-y)}, then dydx\frac{dy}{dx} is equal to:

Solution

✅ Correct Option: 2

Given the equation xy=e(x−y)xy = e^{(x-y)}

Using implicit differentiation with respect to xx, treating yy as a function of xx.


The left side, using the product rule:

ddx(xy)=x⋅dydx+y⋅1\frac{d}{dx}(xy) = x \cdot \frac{dy}{dx} + y \cdot 1

ddx(xy)=xdydx+y\frac{d}{dx}(xy) = x\frac{dy}{dx} + y


The right side, using the chain rule:

ddx(e(x−y))=e(x−y)⋅ddx(x−y)\frac{d}{dx}(e^{(x-y)}) = e^{(x-y)} \cdot \frac{d}{dx}(x-y)

ddx(e(x−y))=e(x−y)⋅(1−dydx)\frac{d}{dx}(e^{(x-y)}) = e^{(x-y)} \cdot (1 - \frac{dy}{dx})

ddx(e(x−y))=e(x−y)−e(x−y)⋅dydx\frac{d}{dx}(e^{(x-y)}) = e^{(x-y)} - e^{(x-y)} \cdot \frac{dy}{dx}


Setting both sides equal:

xdydx+y=e(x−y)−e(x−y)⋅dydxx\frac{dy}{dx} + y = e^{(x-y)} - e^{(x-y)} \cdot \frac{dy}{dx}

Collecting all terms with dydx\frac{dy}{dx} on one side:

xdydx+e(x−y)⋅dydx=e(x−y)−yx\frac{dy}{dx} + e^{(x-y)} \cdot \frac{dy}{dx} = e^{(x-y)} - y


Factoring out dydx\frac{dy}{dx}:

dydx(x+e(x−y))=e(x−y)−y\frac{dy}{dx}(x + e^{(x-y)}) = e^{(x-y)} - y

dydx=e(x−y)−yx+e(x−y)\frac{dy}{dx} = \dfrac{e^{(x-y)} - y}{x + e^{(x-y)}}

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