设x+1/x=a（x+1/x）²=x²+1/x²+2x²+1/x²=a²-2∴原方程可变为2（a²-2）-3a-1=02a²-4-3a-1=02a²-3a-5=0（a+1）（2a-5）=0∴a=-1 a=5/2当a=1时x+1/x= -1x²+x+1=0△=1...