Question

已知xx-5x+1=0,求xxxx+1／xx的值

Answer 1

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