08/09/19 11:42:06
>>535-537
(-1+∑[j=1,n]x[j]x[j+1])^2 (x[n+1]=x[1])
=1-2∑[j=1,n]x[j]x[j+1]+(∑[j=1,n]x[j]x[j+1])^2
=(∑[j=1,n]x[j])^2-2∑[j=1,n]x[j]x[j+1]+(∑[j=1,n]x[j]x[j+1])^2
=∑[j=1,n]x[j]^2+2∑[1≦i＜j-1≦n]x[i]x[j]+(∑[j=1,n]x[j]x[j+1])^2
＞∑[j=1,n]x[j]^2