Okay- finally the Wikipedia entry tells it like it is:
“Multiplication of two negative numbers yields a positive result: (-3) B7 (-4) = 12. This situation cannot be understood as repeated addition, and the analogy to debts doesn’t help either. The ultimate reason for this rule is that we want the distributive law to work:
(3 + (-3)) * (-4) = 3 * (-4) + (-3) * (-4).
The left hand side of this equation equals 0 * (-4) = 0. The right hand side is a sum of -12 + (-3) * (-4); for the two to be equal, we need (-3) * (-4) = 12.
Actually, the first site on the history of negative numbers mentions this,
but in a more confusing way.
posted at 15:54 on Sun, 07 Mar, 2004 |
path: /work
All material copyrighted by Jen Schellinck. All rights reserved.