应该是a^2-3a+1=0a^2-3a+1=0等式两边同除以aa-3+1/a=0a+1/a=3a^2+1/a^2=(a+1/a)^2-2=3^2-2=7(a-1/a)^2=(a+1/a)^2-4=3^2-4=5
是a^2-3a+1=0吧除以a，得：a-3+1/a=0a+1/a=3平方，得：a^2+2+1/a^2=9a^2+1/a^2=7(a-1/a)^2=a^2-2+1/a^2=7-2=5
