微分方程解答2ydx-3xy^2dx-xdy=0(化成全微分)y"=(y')^3+y'(高阶方程)
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微分方程解答
2ydx-3xy^2dx-xdy=0(化成全微分)
y"=(y')^3+y'(高阶方程)
2ydx-3xy^2dx-xdy=0(化成全微分)
y"=(y')^3+y'(高阶方程)
![微分方程解答2ydx-3xy^2dx-xdy=0(化成全微分)y](/uploads/image/z/5601103-7-3.jpg?t=%E5%BE%AE%E5%88%86%E6%96%B9%E7%A8%8B%E8%A7%A3%E7%AD%942ydx-3xy%5E2dx-xdy%3D0%28%E5%8C%96%E6%88%90%E5%85%A8%E5%BE%AE%E5%88%86%EF%BC%89y%22%3D%28y%27%29%5E3%2By%27%28%E9%AB%98%E9%98%B6%E6%96%B9%E7%A8%8B%EF%BC%89)
1.∵2ydx-3xy²dx-xdy=0 ==>2xydx-3x²y²dx-x²dy=0 (等式两端同乘以x)
==>yd(x²)-x²dy=y²d(x³)
==>(yd(x²)-x²dy)/y²=d(x³)
==>d(x²/y)=d(x³)
∴x²/y=x³+C (C是积分常数)
2.设y'=p,则y''=pdp/dy
∴pdp/dy=p³+p ==>p(dp/dy-p²-1)=0
∵当p=0时,得y=C1 (C1是积分常数)
当dp/dy-p²-1=0时,
得dp/dy=p²+1 ==>arctanp=y+C2 (C2是积分常数)
==>p=tan(y+C2)
==>cos(y+C2)dy/sin(y+C2)=dx
==>d(sin(y+C2))/sin(y+C2)=dx
==>ln|sin(y+C2)|=x+ln|C3| (C3是积分常数)
==>sin(y+C2)=C3e^x
∴原微分方程的解是:y=C1 (C1是积分常数)
或 sin(y+C2)=C3e^x (C2和C3是积分常数)
==>yd(x²)-x²dy=y²d(x³)
==>(yd(x²)-x²dy)/y²=d(x³)
==>d(x²/y)=d(x³)
∴x²/y=x³+C (C是积分常数)
2.设y'=p,则y''=pdp/dy
∴pdp/dy=p³+p ==>p(dp/dy-p²-1)=0
∵当p=0时,得y=C1 (C1是积分常数)
当dp/dy-p²-1=0时,
得dp/dy=p²+1 ==>arctanp=y+C2 (C2是积分常数)
==>p=tan(y+C2)
==>cos(y+C2)dy/sin(y+C2)=dx
==>d(sin(y+C2))/sin(y+C2)=dx
==>ln|sin(y+C2)|=x+ln|C3| (C3是积分常数)
==>sin(y+C2)=C3e^x
∴原微分方程的解是:y=C1 (C1是积分常数)
或 sin(y+C2)=C3e^x (C2和C3是积分常数)
微分方程解答2ydx-3xy^2dx-xdy=0(化成全微分)y"=(y')^3+y'(高阶方程)
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