Question

已知x+x的负一次方=3,求x的平方减x的负二次方的值

Answer 1

x+1/x=3

x²+1/x²+2=9

x²+1/x²=7

x²+1/x²-2=5

(x-1/x)²=5

x-1/x=±√5

x²-1/x²=(x+1/x)(x-1/x)=±3√5