即a²-3a+1=0
所以a²=3a-1
a²+1=3a
所以原式=2(3a-1)-5a-2+3/3a
=6a-2-5a-2+1/a
=a-4+1/a
=(a²+1)/a-4
=3a/a-4
=3-4
=-1=a-4+1/a=(a²+1)/a-4=3a/a-4这个不明白a²+1=3a采纳吧