a2-3a+1=0,a-3+1/a=0,a+1/a=3,由此可知,a>0.
(a+1/a)^2=a^2+2+1/a^2=9
a^2-2+1/a^2=5,(a-1/a)^2=5,a-1/a=根号5或-根号5.
a^2+1/a^2=7,(a^2-1/a^2)^=(a^2+1/a^2)^2-4=49-4=45
a^2-1/a^2=3根号5或-3根号5.
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