2006-11-03 02:01:35 · 7 answers · asked by Red Falcon 1 in Science & Mathematics ➔ Mathematics
use the number line concept
2006-11-03 02:06:49 · answer #1 · answered by raj 7 · 0⤊ 1⤋
Well, a proof doesn't seem so difficult. Let x and y be any two positive numbers. Let n = -y, which is a negative number.
Trivially, xy = xy, therefore xy - xy = 0. Since n = -y, then xy + ny = 0. And, since we know the xy (being two positive numbers) must be positve, it follows that ny must be negative.
Now that you know that the product of a positive number and a negative number is negative, you can use a proof essentially identical to the above to prove the product of a negative number and a negative number is positive.
2006-11-03 02:37:17 · answer #2 · answered by Anonymous · 1⤊ 0⤋
A mathematical proof is long with some confusing notation not easily done in Y!A. Here's a simple example-based demonstration.
If you add (positive) 3 apples to a stack 5 times (multiplication), you have added (POSITIVE) 15 apples.
If you remove (negative) 3 apples to a stack 5 times (multiplication), you have added (NEGATIVE) 15 apples.
Now undoing is an act of negation.
If you undo (negative) adding (positive) 3 apples to a stack 5 times (multiplication), you have removed (NEGATIVE) 15 apples.
If you undo (negative) removing (negative) 3 apples to a stack 5 times (multiplication), you have added (POSITIVE) 15 apples.
Undoing effectively negates the number of time an action was done. I hope this helps.
2006-11-03 02:14:28 · answer #3 · answered by novangelis 7 · 0⤊ 1⤋
My fifth grade math teacher taught me that minus times plus equals minus, and that minus times minus equals plus. I have put this thoery to the test many times and how found out that it is true. Any time that I took a minus times a plus and got an answer that was a plus, I got the question counted wrong. The same was true for minus times minus. If I came up with an answer that was a minus, it was wrong. After years of experimenting with these problems, I have reached the conclusion that it is 100% correct due to the repeated identical conclusions I have noted. In other words, "CAUSE THE TEACHER SAID SO, DUMMY".
2006-11-03 02:09:52 · answer #4 · answered by Anonymous · 0⤊ 0⤋
it has a very simple proof.
what will u get if u remove "-" from "+" a "-"
and what if u add "-" and "-" u get a "+".
so this was the concept used by mathematicians to prove this
2006-11-03 02:13:33 · answer #5 · answered by ctenophora 2 · 0⤊ 1⤋
numberline is the best resourse
2006-11-03 02:08:03 · answer #6 · answered by utnip123 2 · 0⤊ 1⤋
- means opposite
I know it's confusing.
2006-11-03 02:09:10 · answer #7 · answered by ♥honey♥ 4 · 0⤊ 1⤋