Why does multiplying two negative numbers equal a positive number?
In: 1210
If you think of the two numbers in a multiplication as (A) the size of step you take on a line and (B) the number of steps you take on a line then…
2×5 means each step is two units long, and you’re taking 5 steps, so you move forward ten units.
-2×5 means each step is two units long, but the minus means you’re pointed the opposite direction on your line. You still take 5 steps. So you move ten units in the opposite direction.
2x-5 means you’re facing the original direction and your steps are two units long. But this time each of the five steps you take is a backwards step. So you move ten units backwards.
Finally…
-2x-5 means you turn to point yourself backwards for your two unit steps but then you take 5 backwards steps. This moves you ten units just the same as if you had just walked forward to begin with.
TLDR: “walk forward” moves you to the same place as “turn around and walk backward” as long as the number and size of the steps are the same.
Latest Answers