适当变换求通解

如题所述

解:∵xy'+y=y(lnx+lny)
==>(xy)'=yln(xy)
==>d(xy)/dx=(xy)ln(xy)/x
==>d(xy)((xy)ln(xy))=dx/x
==>d(ln(xy))/ln(xy)=dx/x
==>∫d(ln(xy))/ln(xy)=∫dx/x
==>ln│ln(xy)│=ln│x│+ln│C│ (C是非零常数)
==>ln(xy)=Cx
==>lny+lnx=Cx
==>lny=Cx-lnx
∴此方程的通解是lny=Cx-lnx。
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