y' = a*y^2 +b*y +c
dy/dx=a*y^2 +b*y +c
dy/a*y^2 +b*y +c=dx
1/[根号（ac-b^2)]arctan(y+b/2a)=x+D,(D为常数)
y=tan[(x+D)*根号（ac-b^2)]-b/2a,(D为常数)
楼主验证一下,应该是对的!