13.设sk=xx x2k … xnk,k=0,1,2,…a=Si j-2,i,j=1.2.…,n.证 13.设sk=xx x2k … xnk,k=0,1,2,…a=Si j-2,i,j=1.2.…,n.证 发布时间:2025-08-20 08:11:49