x²-3x+1=0两边同时除以x得x+1/x=3x+1/x=3两边同时平方得x²+1/x²=9-2=7
x²-3x+1=0x-3+1/x=0x+1/x=3x^2+1/x^2=(x+1/x)^2-2=9-2=7
