式子转化:y^2+x^2(dy/dx)=xy(dy/dx)y^2+x^2(dy/dx)=xy(dy/dx) 原方程可写成dy/dx=y^2/(xy-x^2) 对怎么分离dy/dx和y^2/(xy-x^2) 能说下吗,

来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/23 15:43:19
式子转化:y^2+x^2(dy/dx)=xy(dy/dx)y^2+x^2(dy/dx)=xy(dy/dx)原方程可写成dy/dx=y^2/(xy-x^2)对怎么分离dy/dx和y^2/(xy-x^2)

式子转化:y^2+x^2(dy/dx)=xy(dy/dx)y^2+x^2(dy/dx)=xy(dy/dx) 原方程可写成dy/dx=y^2/(xy-x^2) 对怎么分离dy/dx和y^2/(xy-x^2) 能说下吗,
式子转化:y^2+x^2(dy/dx)=xy(dy/dx)
y^2+x^2(dy/dx)=xy(dy/dx) 原方程可写成dy/dx=y^2/(xy-x^2) 对怎么分离dy/dx和y^2/(xy-x^2) 能说下吗,

式子转化:y^2+x^2(dy/dx)=xy(dy/dx)y^2+x^2(dy/dx)=xy(dy/dx) 原方程可写成dy/dx=y^2/(xy-x^2) 对怎么分离dy/dx和y^2/(xy-x^2) 能说下吗,
dy/dx=y^2/(xy-x^2),分子分母同时除以x^2
即dy/dx=(y/x)^2 / (y/x -1)
这时令y/x=u,
那么y=ux,所以dy/dx=u+x*du/dx,
代入得到u+x*du/dx= u^2/(u-1),
即x*du/dx=u/(u-1),
所以(1 -1/u)*du=1/x *dx,
两边积分得到u-lnu =lnx+C,(C为常数)
即u=ln(ux),带回y/x=u,
故y/x=lny+C,(C为常数) 隐函数也不必再化简了
对于这种可以转换得到dy/dx=f(y/x)形式的微分方程称为齐次方程,
就是要令u=y/x,这样转换来解