Quadratic Equation in one unknown (S4 math problem)

題目是否應為:
2(x^2+(1/x^2))+7(x-(1/x))-1=0

若是,
let y=x-1/x
then y^2=x^2-2+1/x^2
LHS=2(y^2+2)+7y-1=0
2y^2+7y+3=0

The remaining steps are straightforward.

2(x^+(1/x^))+7(x-(1/x))-1=0

question有問題=.=