x^2-3x+1=0
显然x≠0
这样,有:
x^2+1=3x,两边同除以x,得
x+1/x=3
所以 x^2+1/x^2=(x+1/x)^2-2=3^2-2=7
x^3+1/x^3=(x+1/x)(x^2-1+1/x^2)=3*(7-1)=18
∵x²-3x+1=0
∴x=﹙3±√5﹚/2
1/x=﹙3-﹤±√5﹥﹚/2
∴x+1/x=3
x²+1/x²=﹙x+1/x﹚²-2=3²-2=7
x³+1/x³=﹙x+1/x﹚﹙x²+1/x²-1﹚=3×﹙﹤x+1/x﹥²-2-1﹚=3×﹙3²-3﹚=18