`\frac{1}{x}+9+(-\frac{1}{x})+(-\frac{1}{2})<0` `(`đk : `xne0)`

`<=>\frac{1}{x}+9-\frac{1}{x}-\frac{1}{2}<0`

`<=>9-\frac{1}{2}<0`

`<=>17/2<0` `(` vô lí `)`

Vậy `x in emptyset`