3A=3X2+6XY+3X-3 2B=-2X2-2XY+2Y3A-2B=5X2+8XY+3X-3-2Y =5X2+3X-3甲:1.5X乘以0.8+900乙:1.5X+900X0.61500份甲=2250X0.8+900=2700乙:2250+540=2790
哪题?