(x减x分之1)的平方等于2分之1
(x-1/x)^2=1/2
(x^2-1)^2=x/2
x^2-2x+1-x/2=0
x^2-5x/2+1=0
x^2-5x/2+(5/4)^2=-1
(x-5/4)^2=9/16
x-5/4=±3/4
x1=2 x2=1/2 .