x+1/x=2根号5 则x-1/x等于多少_数学解答

x+1/x=2根号5 则x-1/x等于多少

人气：471 ℃　时间：2020-05-24 08:35:17

解答

x+1/x=2√5.
(x+1/x)^2=20.
(x^2+2+1/x^2=20.
x^2+1/x^2=18.
(x^2-2+1/x^2=18-2.
( x-1/x)^2=16.
x-1/x=±4.