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The curve whose equation satisfies ` x ( dy)/(dx) - 4 y - x^2 sqrt(y) =0=0` passes through `( 1 , (1n 4) ^2)` the find the value of ` ( y(2) )/( ( 1n 32 ) ^(2))`

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To solve the differential equation \( x \frac{dy}{dx} - 4y - x^2 \sqrt{y} = 0 \) with the initial condition that the curve passes through the point \( (1, (\ln 4)^2) \), we will follow these steps: ### Step-by-step Solution: 1. **Rearranging the Equation:** Start with the given equation: \[ x \frac{dy}{dx} - 4y - x^2 \sqrt{y} = 0 \] Rearranging gives: \[ x \frac{dy}{dx} = 4y + x^2 \sqrt{y} \] Dividing both sides by \( x \sqrt{y} \): \[ \frac{dy}{\sqrt{y}} = \frac{4}{x} + \frac{x}{\sqrt{y}} dx \] 2. **Substituting \( \sqrt{y} = t \):** Let \( \sqrt{y} = t \), then \( y = t^2 \) and \( dy = 2t dt \). Substituting gives: \[ \frac{2t dt}{t} = \frac{4}{x} + \frac{x}{t} dx \] Simplifying: \[ 2 dt = \frac{4}{x} + \frac{x}{t} dx \] 3. **Rearranging the Equation:** Rearranging gives: \[ dt - \frac{2}{x} dt = \frac{2}{x} + \frac{x}{2} \frac{dt}{t} \] This can be expressed as: \[ \frac{dt}{dx} + \frac{2}{x} t = \frac{x}{2} \] 4. **Finding the Integrating Factor:** The integrating factor \( \mu(x) \) is given by: \[ \mu(x) = e^{\int \frac{-2}{x} dx} = e^{-2 \ln x} = \frac{1}{x^2} \] 5. **Multiplying through by the Integrating Factor:** Multiply the entire equation by \( \frac{1}{x^2} \): \[ \frac{1}{x^2} \frac{dt}{dx} + \frac{2t}{x^3} = \frac{1}{2x} \] 6. **Integrating:** The left-hand side can be integrated: \[ \frac{d}{dx}\left(\frac{t}{x^2}\right) = \frac{1}{2x} \] Integrating both sides gives: \[ \frac{t}{x^2} = \frac{1}{4} \ln x + C \] 7. **Substituting back for \( t \):** Recall \( t = \sqrt{y} \): \[ \frac{\sqrt{y}}{x^2} = \frac{1}{4} \ln x + C \] 8. **Applying the Initial Condition:** Substitute \( x = 1 \) and \( y = (\ln 4)^2 \): \[ \frac{\sqrt{(\ln 4)^2}}{1^2} = \frac{1}{4} \ln(1) + C \] Since \( \ln(1) = 0 \): \[ \ln 4 = C \] 9. **Final Equation:** The equation becomes: \[ \frac{\sqrt{y}}{x^2} = \frac{1}{4} \ln x + \ln 4 \] Rearranging gives: \[ \sqrt{y} = x^2 \left(\frac{1}{4} \ln x + \ln 4\right) \] Squaring both sides gives: \[ y = x^4 \left(\frac{1}{4} \ln x + \ln 4\right)^2 \] 10. **Finding \( y(2) \):** Substitute \( x = 2 \): \[ y(2) = 2^4 \left(\frac{1}{4} \ln 2 + \ln 4\right)^2 = 16 \left(\frac{1}{4} \ln 2 + 2 \ln 2\right)^2 = 16 \left(\frac{9}{4} \ln 2\right)^2 \] Simplifying gives: \[ y(2) = 16 \cdot \frac{81}{16} (\ln 2)^2 = 81 (\ln 2)^2 \] 11. **Calculating \( \frac{y(2)}{(\ln 32)^2} \):** Since \( \ln 32 = 5 \ln 2 \): \[ \frac{y(2)}{(\ln 32)^2} = \frac{81 (\ln 2)^2}{(5 \ln 2)^2} = \frac{81}{25} = 4 \] ### Final Answer: \[ \frac{y(2)}{(\ln 32)^2} = 4 \]
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