Question:medium

Let \(e^{\alpha y} + e^{\beta y} + \gamma x^2 + \delta \log|x| + C = 0\), where \(C \in \mathbb{R}\) be a particular solution of the differential equation \(x(e^{2y} - 1)dy + (x^2 - 1)e^y dx = 0\) and passes through the point (1, 1). The value of \((\alpha + \beta + \gamma + \delta - C)\) is

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For variable separable differential equations, the main goal is to isolate all 'y' terms with 'dy' and all 'x' terms with 'dx' on opposite sides of the equation. Be careful with algebraic manipulations, especially with negative signs and logarithms.
Updated On: Mar 27, 2026
  • \(e - 1\)
  • \(e^2 - 1\)
  • \(e + \frac{1}{e}\)
  • \(\frac{1}{e}\)
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The Correct Option is C

Solution and Explanation

Objective: Solve a first-order differential equation. This involves finding the general solution using separation of variables, determining the particular solution using a given point (1, 1), and then comparing coefficients with a specified form to find \(\alpha, \beta, \gamma, \delta\), and C. Finally, compute the expression \((\alpha + \beta + \gamma + \delta - C)\).
Differential Equation:\[ x(e^{2y} - 1)dy + (x^2 - 1)e^y dx = 0 \]Method: Separation of variables. Rearrange, group terms, integrate, and apply the initial condition.Solution Process:
1. Rearrange the equation: \(x(e^{2y} - 1)dy = -(x^2 - 1)e^y dx\)
2. Separate variables: \(\frac{e^{2y} - 1}{e^y} dy = -\frac{x^2 - 1}{x} dx\)
3. Simplify: \((e^y - e^{-y}) dy = -(x - \frac{1}{x}) dx\)
4. Integrate both sides: \(\int (e^y - e^{-y}) dy = -\int (x - \frac{1}{x}) dx\)
5. Perform integration: \(e^y + e^{-y} = -\left(\frac{x^2}{2} - \log|x|\right) + K\), where K is the constant of integration.
6. Rewrite the general solution: \(e^y + e^{-y} + \frac{1}{2}x^2 - \log|x| - K = 0\)
7. Compare with the given form \(e^{\alpha y} + e^{\beta y} + \gamma x^2 + \delta \log|x| + C = 0\) to find: \(\alpha = 1\), \(\beta = -1\), \(\gamma = \frac{1}{2}\), \(\delta = -1\), \(C = -K\).
8. Use the point (1, 1) to find K: \(e^1 + e^{-1} + \frac{1}{2}(1)^2 - \log|1| = K \implies K = e + \frac{1}{e} + \frac{1}{2}\).
9. Determine C: \(C = -K = -\left(e + \frac{1}{e} + \frac{1}{2}\right)\).
10. Compute the expression \((\alpha + \beta + \gamma + \delta - C)\): \(\left(1 + (-1) + \frac{1}{2} + (-1)\right) - \left(-\left(e + \frac{1}{e} + \frac{1}{2}\right)\right) = -\frac{1}{2} + e + \frac{1}{e} + \frac{1}{2} = e + \frac{1}{e}\).
Result: The value of \((\alpha + \beta + \gamma + \delta - C)\) is \(e + \frac{1}{e}\).
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