问题 填空题 如果单项式35xm-1y2n与54x3yn+3是同类项,那么mn=______. 答案 ∵35xm-1y2n与54x3yn+3是同类项,∴m-1=3,2n=n+3,解得:m=4,n=3,∴mn=4×3=12.故答案为:12.