Negative Multiplication ```Name: Mehdi Status: N/A Age: N/A Location: N/A Country: N/A Date: N/A ``` Question: How do you explain -1*-1=+1 (without using velocity, direction and time) Replies: Multiplication by -1 is reflection through the origin. A number becomes its counterpart on the other side of zero. Clearly, if you reflect a number twice through the origin (multiply twice by -1), then that is the same as doing nothing at all (multiplying once by 1). Grayce Hello, My guess is that this is a concept, a convention, an assumption, or an agreement, based on which other relationships can be expressed and derived. I recommend looking into a reference book on the history of mathematics to learn about its invention and justifications. AK Dr. Ali Khounsary Click here to return to the Mathematics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012