简单分析一下，详情如图所示
e^(xy)(y+xy')+2yy'=-sinx [xe^(xy)+2y]y'= -sinx-ye^(xy) y'= -[sinx + ye^(xy)]/[2y+xe^(xy)] dy = -[sinx + ye^(xy)]dx / [2y+xe^(xy)]
