$$\left( 2 , 7 \right) , \left( 8 , -3 \right) , \left( - \frac{ 1 }{ 2 } , -2 \right) , \left( 0 , 0 \right)$$
$\left(2,7\right),\left(8,-3\right),\left(-\frac{1}{2},-2\right),\emptyset$
