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The solution of the differential equation dydx=x2+xy+y2x2\dfrac{dy}{dx} = \dfrac{x^2+xy+y^2}{x^2} for x>0,y>0x>0, y>0 at x=1,y=2x=1, y=2 is

Solution

✅ Correct Option: 3

The equation is homogeneous. Putting y=vxy=vx gives v+xdvdx=1+v+v2v+x\frac{dv}{dx}=1+v+v^2, so dv1+v2=dxx\frac{dv}{1+v^2}=\frac{dx}{x} and tan⁡−1v=log⁡ex+C\tan^{-1}v=\log_e x+C. Using x=1,y=2x=1,y=2 gives C=tan⁡−12C=\tan^{-1}2, hence tan⁡−1yx=log⁡ex+tan⁡−12\tan^{-1}\frac{y}{x}=\log_e x+\tan^{-1}2.

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