∵a²-3a+1=0
∴2a²-6a+2=0
∴2a²-5a=a-2
∵a²-3a+1=0
∴a²+1=3a
2a²-5a-2-3/(1+a²)
=a-2-2+3/3a
=a-4+1/a
=(a²+1-4a)/a
=(3a-4a)/a
=-a/a
=-1
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