What are the value of α and β that make \(dF(x, y)=\left(\frac{1}{x^2+2}+\frac{\alpha}{y}\right)dx\space + (xy^\beta+1)dy\) an exact differential equation?

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UPSC IES Electrical 2022 Prelims Official Paper
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  1. α = -1, β = -2
  2. α = 1, β = -2
  3. α = -1, β = 2
  4. α = -2, β = -1

Answer (Detailed Solution Below)

Option 1 : α = -1, β = -2
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Detailed Solution

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Concept:

Consider an exact differential equation:

M dx + N dy = 0

The condition of an exact differential equation:

\({\partial M\over \partial y}={\partial N\over \partial x}\)

Calculation:

Given, \(dF(x, y)=\left(\frac{1}{x^2+2}+\frac{\alpha}{y}\right)dx\space + (xy^\beta+1)dy\)

\(M=\frac{1}{x^2+2}+\frac{\alpha}{y}\) and \(N=(xy^\beta+1)\)

\(-\alpha y^{-2}=y^\beta\)

α = -1, β = -2

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