x^2-5x+1=0
方程两边同除以x
x-5+1/x=0
x+1/x=5
(x^4+1)/x^2
=x^2+1/x^2
=(x+1/x)^2-2
=5^2-2
=25-2
=23
方可以用“^”表示(x^4+1)/x^2=x^2+1/x^2=(x+1/x)^2-2这儿能说明下吗？这很简单啊。(x^4+1)/x^2=(x^4/x^2)+(1/x^2)=x^2+1/x^2=(x+1/x)^2-2