题目若单项式−12xm−2y5-\frac{1}{2}{x}^{m-2}{y}^{5}−21xm−2y5与2xy2n+12xy^{2n+1}2xy2n+1的和仍为单项式,则∣n−m∣=______.|n-m|= \_\_\_\_\_\_.∣n−m∣=______.知识点：合并同类项章节：数与式 / 代数式
