因为a是方程x²+1=3x的根所以a²+1=3a所以1=3a-a²所以a³-2a²-5a+1/a²+1=(a³-2a²-5a+3a-a²)/(a²+3a-a²)=(a³-3a²-2a)/3a=a(a²-3a-2)/3a=a(-1-2)...