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Résoudre sur \((\R^{+*})^2\) : \(x\frac{\partial f}{\partial x} = y\frac{\partial f}{\partial y}\), en posant \(\begin{cases} u = xy \cr v = \frac xy. \end{cases}\)
Résoudre sur \((\R^{+*})^2\) : \(x\frac{\partial f}{\partial x} = y\frac{\partial f}{\partial y}\), en posant \(\begin{cases} u = xy \cr v = \frac xy. \end{cases}\)