Question

x的平方-3x+1=0求x3次方+x3次方分之一的值

Answer 1

x^2-3x+1=0

x^2+1=3x

x+1/x=3

(x+1/x)^2=9

x^2+2+1/x^2=9

x^2+1/x^2=7

x^3+1/x^3=(x+1/x)(x^2-1+1/x^2)=3x(7-1)=18