±3 x ±1

$${\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{1}} = {\mathtt{3}}$$

$$\left(-{\mathtt{3}}\right){\mathtt{\,\times\,}}\left(-{\mathtt{1}}\right) = {\mathtt{3}}$$

$$\left(-{\mathtt{3}}\right){\mathtt{\,\times\,}}{\mathtt{1}} = -{\mathtt{3}}$$

$${\mathtt{3}}{\mathtt{\,\times\,}}\left(-{\mathtt{1}}\right) = -{\mathtt{3}}$$

 

So, ±3 x ±1 = 3, -3