(1)x-1/x=-2(x-1/x)²=(-2)²x²+1/x²-2=4x²+1/x²=6 (2)x²-3x+1=0x-3+1/x=0(除以x得）x+1/x=3(x+1/x)²=3²x²+1/x²+2=9x²+1/x²=7