y'+y+lnx=ax
dy/dx=-y+ax-lnx
dy/dx=-y
lny=ln1/x+C0
y=C/x
设y=C(x)/x
C'(x)/x=ax-lnx
dC(x)=ax^2dx-xlnxdx ∫xlnxdx=lnx*x^2/2-(1/2)∫xdx=x^2lnx/2-x^2/4+C
C(x)=ax^3/3-(x^2lnx)/2+x^2/4+C1
通解为y=ax^2/3-xlnx/2+x/4+C1/x