Negative times Negative: A Deep Dive into Understanding It
A video by James Tanton looking into how you can show that a negative times a negative must be equal to a positive number.
Hi Friends
Thought that you and your math-loving-kid would enjoy the following video:
Description:
It's an age-old question: Why is negative times negative positive? And school mathematics is not prepared to give a proper justification as the proclivity there, for fine reasons perhaps, is to seek real world models that "explain" math. (Where in the real world do you actually multiply two negative numbers together? "If I am traveling at a negative velocity and go backwards in time, then I've moved a positive distance forwards." Got that?) Here's the math that leads us to say that negative times negative is positive. It all just hinges on one belief about how numbers work.
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Stay Mathy!
All the best,
Sebastian