x.x-5x+1=0,那么x.x+1/x.x

x^2+1=5x x^4/x^2+1/x^2 (x^4+1)/x^2 {(x^2+1)(x^2-1)+2}/x^2 代入x^2+1=5x 5x.(5x-2)+2/x^2 (25x^2-10x+2)/x^2 10x=2x^2+2 (25x^2-2x^2-2+2/x^2 答案是23 我没笔全靠脑子模拟的有错误抱歉了