(2+4+6+8+...2n)-{1+3+5+7+...+(2n-1)}

问题描述:

(2+4+6+8+...2n)-{1+3+5+7+...+(2n-1)}

(2+4+6+8+...2n)-{1+3+5+7+...+(2n-1)} =(2-1)+(4-3)+……+{2n-(2n-1)}=1*n=n