We are given a first-order differential equation and we are asked to solve it. The equation is $y' = \frac{y^2}{xy - x^2}$.

AnalysisDifferential EquationsFirst-order Differential EquationHomogeneous Differential EquationSeparation of Variables
2025/4/29

1. Problem Description

We are given a first-order differential equation and we are asked to solve it. The equation is y=y2xyx2y' = \frac{y^2}{xy - x^2}.

2. Solution Steps

The given differential equation is y=y2xyx2y' = \frac{y^2}{xy - x^2}.
We can rewrite this as y=y2x(yx)y' = \frac{y^2}{x(y - x)}. This is a homogeneous differential equation, so we can use the substitution y=vxy = vx, where vv is a function of xx.
Then, y=v+xvy' = v + xv'. Substituting these into the equation, we have
v+xv=(vx)2x(vxx)=v2x2x2(v1)=v2v1v + xv' = \frac{(vx)^2}{x(vx - x)} = \frac{v^2x^2}{x^2(v - 1)} = \frac{v^2}{v - 1}.
Then, xv=v2v1v=v2v(v1)v1=v2v2+vv1=vv1xv' = \frac{v^2}{v - 1} - v = \frac{v^2 - v(v - 1)}{v - 1} = \frac{v^2 - v^2 + v}{v - 1} = \frac{v}{v - 1}.
Separating variables, we have v1vdv=dxx\frac{v - 1}{v}dv = \frac{dx}{x}.
Integrating both sides, we get
v1vdv=dxx\int \frac{v - 1}{v}dv = \int \frac{dx}{x}
(11v)dv=dxx\int (1 - \frac{1}{v})dv = \int \frac{dx}{x}
vlnv=lnx+Cv - \ln|v| = \ln|x| + C, where CC is the constant of integration.
Now, we substitute v=yxv = \frac{y}{x}.
yxlnyx=lnx+C\frac{y}{x} - \ln|\frac{y}{x}| = \ln|x| + C
yxlny+lnx=lnx+C\frac{y}{x} - \ln|y| + \ln|x| = \ln|x| + C
yxlny=C\frac{y}{x} - \ln|y| = C
yx=lny+C\frac{y}{x} = \ln|y| + C
y=x(lny+C)y = x(\ln|y| + C)

3. Final Answer

y=x(lny+C)y = x(\ln|y| + C)
yxlny=C\frac{y}{x} - \ln|y| = C

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