Question

已知x+x^(-1)（←x的－1次方）=3,求下列各式的值：

Answer 1

[x^(1/2)+x^(-1/2)]^2=x+x^(-1)+2=5

因此x^(1/2)+x^(-1/2)=根号5

[x^(1/2)-x^(-1/2)]^2=x+x^(-1)-2=1

因此x^(1/2)-x^(-1/2)=正负1