x-1/x=2(x-1/x)^2=4x^2-2+1/x^2=4x^2+1/x^2=4+2=6(x^2+1/x^2)^2=36x^4+2+1/x^4=36x^4+1/x^4=36-2=34
x^4+1/x^4=(x^2-1/x^2)^2+2=[(x-1/x)^2+2]^2+2=(4+2)^2+2=36+2=38
x-1/x=2即平方的：x^2+1/x^2=6再平方的：x^4+1/x^=34
