1) 4x^3y-6x^2y^2= 2x^2y (2x-3y) 2) 5а^3-15а^2b+20ab^2= 5a (a^2-3ab+4b^2) 3) 6mn^2-9n^3+12m^2n^2= 3n^2 (2m-3n+4m^2) 4) -3xy^2-15x^2y-21x^2y^2= -3xy (y+5x+7xy) 5) 12a^2b-18ab^2-30ab^3= 6ab (2a-3b- 5b^2) 6) -6ax^2+9x^2-12x^4-3a^2x^2= 3x^2 (-2a+3-4x^2-3a^2)