常微分dx/dt=y-3x,dy/dt=8x-y怎么求解啊.

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dx/dt=y-3x ①dy/dt=8x-y ②由②/①得：dy/dx=(8x-y)/(y-3x)dy/dx=(8-y/x)/(y/x-3)令y/x=u,则y=ux,dy/dx=u+x·du/dx故u+x·du/dx=(8-u)/(u-3)整理得：dx/x=(u-3)/(-u²+2u+8)du两端同时积分即可求得u和x的关系式...