(x+y)²=9,(x-y)²=4,xy=?
问题描述:
(x+y)²=9,(x-y)²=4,xy=?
答
(x+y)²=9,(x-y)²=4,xy=[(x+y)²-(x-y)²]/4= (9-4)/4=5/4
(x+y)²=9,(x-y)²=4,xy=?
(x+y)²=9,(x-y)²=4,xy=[(x+y)²-(x-y)²]/4= (9-4)/4=5/4