(x-1)(y+1)dx-(x+1)ydy=0

(x-1)dx/(x+1) = ydy/(y+1) (1 - 2/(x+1))dx = (1 - 1/(y+1)) dy проинтегрируем обе части: x - 2ln(x+1) = y - ln(y+1) + C

(ху+х-у-1)dx-xydy-ydy=0 x^2yd+dx^2-ydx-dx-xy^2d-y^2d=0