20.若集合A={a
1,a
2,?,a
n}(0≤a
1<a
2<a
3<?<a
n)滿足:對(duì)任意i,j(1≤i≤j≤n),均存在k,t(1≤k≤n,1≤t≤n),使得(a
j-a
i-a
k)(a
j+a
i-a
t)=0,則稱A具有性質(zhì)P.
(Ⅰ)判斷集合M={0,3,6,9},N={1,4,6,8}是否具有性質(zhì)P;(只需寫出結(jié)論)
(Ⅱ)已知集合A={a
1,a
2,?,a
n}(0≤a
1<a
2<a
3<?<a
n)具有性質(zhì)P.
(?。┣骯
1;
(ⅱ)證明:
.