Question

已知x+1/x=3,求x^2+1/x^2 x^2+1/x^2=(x+1/x)^2-2=9-2=7 (2)借鉴上题的解法求

Answer 1

x^2-5x+1=0

x-5+1/x=0

x+1/x=5

（x+1/x）²=25

x²+2+1/x²=25

x²-2+1/x²=21

（x-1/x）²=21

x-1/x = ±√21