There have been quite a few blog posts lately discussing how one would explain to a "non-math" person why a negative times a negative is a positive. I think the reason we have such a hard time explaining it is because it's not true. We need look no further than California's own Nancy Pelosi for the explanation. (Check right around 3:50)
In an interview with CNBC's Maria Bartiromo, Pelosi was asked if the expiration of the Bush tax cuts would amount to a tax increase.
Her response:
"It's not a tax increase. It is eliminating a tax decrease that was there."
So there you have it--eliminating a decrease does not amount to an increase. I had better go fix those lesson plans. Thanks for clearing things up, Ms. Pelosi.
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2 comments:
Nice!
My personal best I ever did to explain this to myself was:
multiplication by -1 is a rotation in space (ie. a vector space), or a reflection on a number line in a 1D space. Two such multiplications rotate or reflect back to the original position.
This fails the criteria for explanation to a non-mathematician.
The vector works too. I always liked Stand and Deliver's, "Fill the hole Johnny."
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