a�0�5-3a+1=0
a�0�5+1=3a
等号两边同除以a得:a+1/a=3
上式等号两边同时平方得:a�0�5+1/a�0�5=3�0�5-2=7
上式变为:a�0�5-2+1/a�0�5=7-2=5
上式等号两边同时开方得:a-1/a=±√5
解:因为(∵)a�0�5-3a+1=0,所以(∴)a-3+1/a=0,a+1/a=3
又∵(a+1/a)�0�5=a�0�5+2·a·1/a+1/a�0�5=3�0�5
∴a�0�5+2+1/a�0�5=9,a�0�5+1/a�0�5=9-2=7