swissalgebrahelp.com  
Why minus times minus equals plus?Mike Savage gives a brilliant explanation on the excellent British website of mathtutor. I can't but recommend this website heartily. So, why "minus times minus equals plus"? (1)x(1)= 1We have to remember two arithmetics rules:
Then we can now prove that minus x minus = plus.
Let's consider (1)x(2+1) (read "negative one"," times", *two plus one") Now, for rule 2 (above) the operation can be rewritten as = (1)x2 + (1)x(1) so, similarly, we can take another operation such as
(1)x(1+1)and by expanding the brackets (rule 2) we obtain = (1)x(1)+(1)x1
=(1)x(1) 1
But (1)x(1+1) can also be formulated with the rule 1 above (the precedence law, brackets first) as (1)x(1+1)= (1)x(0)Which simply gives =0Now, we combine the two (1)x(1) 1 = 0which is the same to say (1)x(1) = 0 +1and so (1)x(1) = 1Q.E.D. From why minus times minus equals plus back to the study tips webpage
Source, Mike Savage, Mathtutor website

On the shore of a vast sea


Stay in touch with nature. It's full of mathematics! Enjoy This Site?
Then why not use the button below, to add us to your favorite bookmarking service? 

 Homepage About Us Study Tips Contact  This Website is Powered by Site Build It!  and I would never use anything else.


