x²+1/x²+2=16
(x+1/x)²=16
x+1/x=4或-4
(x²+1/x²)(x+1/x)=x³+x+1/x+1/x³=14*4=56 或=14*(-4)=-56
x³+1/x³=56-4=52 或=-56+4=-52
(x²+1/x²)²=x四次方+2+x四次方分之一=196
x四次方+x四次方分之一 =194
(x+1/x)^2=x^2+1/x^2 +2=14+2=16
所以x+1/x=4或-4
x+1/x=4时,x^3+1/x^3=(x+1/x)(x^2+1+1/x^2)=4×(14+1)=56
x+1/x=-4时,x^3+1/x^3=(x+1/x)(x^2+1+1/x^2)=(-4)×(14+1)=-56
x^4+1/x^4=(x^2+1/x^2)-2=14^2 -2=194