x²—ax+2＜0
△=a²-8
1°△≤0,即-2√2≤a≤2√2时,无解
2°△>0,即a≤-2√2或a≥2√2时有解,解为
a/2-√(a²-8)≤x≤ a/2+√(a²-8)
x²-（2a+1）x+a²+1≤0
△=4a-3
1°△¾时,有解
a+½-√(4a-3)