<span>think of numbers as points along a line from - to + infinity, with 0 in the middle.
when we multiply, what we're going to do is find a new place along that line.
we use the first number to pick a place, and the second number to change that place -- to head to a new location.
when we add or subtract, we do the same. pick a place, and then move
along the line, in the direction and distance specified by the 2nd
number.
pick 3, multiply by 2, and you're twice as far along the line.
when you multiply by -2, you change direction, but have the same magnitude.
so you look on the other side of 0, and then go twice as far away from 0, just as you did before.
next, when you're at -4 and multiply by 2, you continue along the line in the same direction, to -8
last, when you're at -3, and multiply by -2, the -2 makes you change
direction, so now you're on the + side of the line, and the 2 makes you
go twice as far, to 6.