what is the logic behind it ? you know when we do minus we move left of no. line and when we add something we move right on no. line , so what do minus minus do to become positive and move right on no. line
Hi,
The most basic operation is that of counting objects. We count 1, +1 more, +1 more, finding a way to identify groups that contain more than one object and call them something else so we can recognize them more quickly 1,2,3,... .
Multiplication is just an extension of counting. If we have 2*3 we are counting 3 objects two times, or counting 2 objects 3 times.
The invention of negative numbers allows us to count in two directions which are opposite to each other. If we count 3 objects to the right and 1 object to the left, we have 3-1 which of course brings us to the second (2) object. So if we have 2*(-3) we are counting three objects in the opposite direction (of normal) twice, or we are counting 2 objects three times in the opposite direction. The result is 6 objects in the opposite direction (of normal).
So if right is normal, if we have (-2)*(-3) then we are counting three objects oriented left two times oriented in the opposite direction, which means we end up counting right (with right being the normal direction).
The rule for two signs in tabular form of course is:
-- = +
+- = -
-+ = -
++ = +
Another interesting question, can we really have zero of something? If we have zero of something, then we already dont have anything to have zero of it of