(1)原式=-9+4-1=-6(2)原式=(-12x4y3)÷(4x2×2y2)?(-3xy)=(-3x0y)?(-3xy)=9xy2(3)原式=[15x3y5÷(-5x3y2)]+[(-10x4y4)÷(-5x3y2)]+[(-20x3y2)÷(-5x3y2)]=-3y3+2xy2+4.