条件应为求证 10
∴xy≤[(x+y)²/4](当且仅当x=y时等号成立)
∴(x+y)²-(x+y)-xy=0
改为(x+y)²-(x+y)-[(x+y)²/4]≥0
3/4*(x+y)²-(x+y)≥0
(x+y)[3/4*(x+y)-1]≥0
∵x>0,y>0
∴(x+y)>0
∴3/4*(x+y)-1≥0
∴0
条件应为求证 10
∴xy≤[(x+y)²/4](当且仅当x=y时等号成立)
∴(x+y)²-(x+y)-xy=0
改为(x+y)²-(x+y)-[(x+y)²/4]≥0
3/4*(x+y)²-(x+y)≥0
(x+y)[3/4*(x+y)-1]≥0
∵x>0,y>0
∴(x+y)>0
∴3/4*(x+y)-1≥0
∴0