What the Heck Is the Zero Product Rule?

The fancy answer is, “For all numbers a and b, ab = 0 implies a = 0 or b = 0.”

The less fancy, and still strange answer is: If two things multiply to get zero, one or both of them better be zero. Like this:

Too much pixie dust, for my taste. What doesn’t work, for sure, is this:

So why does it work with zero and not three?!? To answer this, we need a little background on fractions and zero. And pizza – pizza’s always a good thing to add to math:

Using the fact in the video above, the “foorp” in this video shows why it’s true:

Special thanks to GFC at MyMathForum.com for inspiring this post.