将A带入方程:A^2-3A+1=0,则A^2+1=3A
2A^2-5A-2+3/(A^2+1)
=2(A^2-3A+1)+A-4+3/(A^2+1)
=A-4+3/3A
=A-4+1/A
=-4+(A^2+1)/A
=-4+3A/A
=-4+3
=-1
将A带入方程:A^2-3A+1=0,则A^2+1=3A
2A^2-5A-2+3/(A^2+1)
=2(A^2-3A+1)+A-4+3/(A^2+1)
=A-4+3/3A
=A-4+1/A
=-4+(A^2+1)/A
=-4+3A/A
=-4+3
=-1