x的二次方减3x加1等于0x-3+1/x=0x+1/x=3(x+1/x)^2=9x^2+1/x^2+2=9x^2+1/x^2=7
x^2-3x+1=0方程两边同除以x,得:x-3+1/x=0x+1/x=3(x+1/x)^2=9x^2+2+1/x^2=9x^2+1/x^2=7
