(1) 2x-xdy/dx-y+1+dy/dx=0,
-xdy/dx+dy/dx=-2x+y-1,
(dy/dx)(-x+1)=-2x+y-1,
dy/dx=(y-2x-1)/(1-x) or (2x-y+1)/(x-1).
(2) (a) (d/dx)(exy+x+y-1)=exdy/dx+exy+1+dy/dx=0, dy/dx=-(exy+1)/(ex+1);
(b) (d/dx)(exy+x+y-1)=exy(y+xdy/dx)+1+dy/dx=0, dy/dx=-(exyy+1)/(xexy+1).
(3) 1/x+(1/y)(dy/dx)=1-dy/dx, dy/dx(1+1/y)=1-1/x,
dy/dx=(1-1/x)/(1+1/y)=((x-1)/x)(y/(y+1))=y(x-1)/(x(y+1)).
(4) 3x2+3y2dy/dx+2xy+x2dy/dx+2ydy/dx, dy/dx=-(3x2+2xy)/(3y2+x2+2y).