x²-ax+a+1≥0x²-2×(a/2)x+(a/2)²-(a/2)²+a+1≥0(x-a/2)²-(a/2)²+a+1≥0(2x-a)²/4-(a²-4a-4)/4≥0(2x-a)²-(a²-4a-4)≥0(2x-a)²≥a²-4a-41、当a²-...