(1)f(x)=x^2-(a+1/a)x+1≤0
则 (x-a)(x-1/a)≤0
a=1/2时,即
(x-1/2)(x-2)≤0
1/2 ≤x≤2
2)f(x)=x^2-(a+1/a)x+1≤0
当0