令a=x+1/x则a²=x²+2+1/x²所以即2(a²-2)-3a=12a²-3a-5=0(2a-5)(a+1)=0a=5/2,a=-1x+1/x=5/22x²-5x+2=0(2x-1)(x-2)=0x=1/2,x=2x+1/x=-1x²+x+1=0△