问题 填空题 约分:2a4-4ab=______,-2mn2-8m5n3=______,x2-y2x-y=______. 答案 2a4-4ab=-a32b,-2mn2-8m5n3=14m4n,x2-y2x-y=x+y;故答案为:-a32b,14m4n,x+y.