how to multiply negatives
Whether it is numbers or $\displaystyle x$s you are multiplying the same rules apply.
let $\displaystyle +$ = positive number, and $\displaystyle -$ = negative number.
$\displaystyle +$ x $\displaystyle +$ = $\displaystyle +$
$\displaystyle +$ x $\displaystyle -$ = $\displaystyle -$
$\displaystyle -$ x $\displaystyle +$ = $\displaystyle -$
$\displaystyle -$ x $\displaystyle -$ = $\displaystyle +$
Two of the same, ie two plus's or two minus' always equal a plus, and two different ones always equal a minus.
Hope this makes sense