Posted by haifeng on 2016-04-02 23:52:55 last update 2016-04-02 23:58:24 | Answers (0) | 收藏
求
\[ \frac{y}{x}\cdot\frac{dy}{dx}=\frac{1+x^2 y^2}{1-x^2 y^2} \]
令 $u=x^2$, $v=y^2$, 则方程化为一阶非线性常微分方程:
\[ \frac{dv}{du}=\frac{1+uv}{1-uv}. \]
