can anyone tell me why negative * negative is positive?associated wid integers.?

Answer 1

That's a great question! It's too bad so many people answered, "that's just the way it is, don't fight it." In my opinion, the only way you can ever enjoy math and get good at it is too discover how and why it makes sense. If you look at math as just a set of incomprehensible rules to memorize, you'll never really get past basic arithmetic. So, I applaud your persistence in wanting to know "why".

The short answer to your question is this: (neg)*(neg)=(pos) is the only convention that is consistent with all the other sensible rules.

Here's what I mean:

Rule 1: (pos)*(pos) = (pos)
That rule makes sense; it's what we all grew up with.

Rule 2: (pos)*(neg) = (neg)
That rule makes sense too, when you look at multiplication as repeated addition. For example, take (3)(-4). Supposedly this should be the same as adding (-4) to itself, three times; like this: (-4)+(-4)+(-4). And we know that adding a negative number always makes you move toward the LEFT on the number line; so we should expect (-4)+(-4)+(-4)=–12. Therefore, it makes sense that (3)(-4)=–12.

Rule 3: (neg)*(pos) = (neg)
This rule is just like Rule 2. In multiplication, we expect to be able to switch the two factors around without changing the result. So, if (3)(-4)=–12, we expect that (-4)(3)=–12 as well.

Now consider a division rule:

Rule 4: (pos)/(neg) = ???

There are only two possibilities: either (pos)/(neg) = (pos); or (pos)/(neg) = (neg). Let's see which one makes sense.

Suppose (pos)/(neg) = (pos). Specific example: (30)/(-5) =? (6).
Multiply both sides by (-5):
[(30)/(-5)](-5) =? (6)(-5)

On the left side, the (-5) should cancel out, by the normal rules of multiplication and division, so:
30 =? (6)(-5)

But that says that (pos) = (pos)*(neg), which conflicts with Rule 2. So our guess that (pos)/(neg) = (pos) does not make sense. So, to make sense with the other rules, we should say that (pos)/(neg) = (neg):

Rule 4: (pos)/(neg) = (neg)

And now we are ready to tackle (neg)*(neg).

From Rule 4, we know this is true: (20)/(-4) = (-5).

Multiply both sides by (-4):
[20/(-4)](-4) = (-5)(-4)

The (-4) cancels out on the left side:
20 = (-5)(-4)

And this demonstrates the rule:

Rule 5: (neg)*(neg) = (pos)

Answer 2

One thing you have to realize is that a negative number is just a positive number that has been multiplied by a negative 1.

It's just something that had to have been accepted in order not to break other rules is math.

what is -1*-1 = -1, what would that break?

Let's see the basic distributive property, and what would happen to it if -1*-1 not eq +1

(-1)(1 + -1) = (-1)(1) + (-1)(-1)

(-1)(0) = -1 + -1

0 = -2
The law is broken and all mathematical hell will brake loose, so It's a law that probably at the time, conformed nicly to other laws and improved upon them

Hope this helps

Here is the link to the explanation

http://mathforum.org/dr.math/faq/faq.negxneg.html

Answer 3

Hi,
This is a mathematical convention. It does have some analogy in language. For example, to say, "It is not, not raining." means that it is raining.
The principal reason for the mathematical convention is that some properties of math would not work if the answer were other than -1*(-1) = 1. Let's assume that -1(-1) = -1 and see where that leads us.
-1(-1+1) = -1(1 + (-1)(-1)
-1 +1 = -1 -1
0 = -2
Making other assumptions will also result in problems. So, there's actually only one answer that won't get us into problems and that's -1(-1) = +1.

Hope this helps a little.
FE

Answer 4

You could demonstrate the truth of the matter through the equation
(A - B)(C - D) = AC - AD - BC + BD
Draw a rectangle. Label one side A, the other C. Now draw another rectangle inside the first one. You do this by drawing two perpendicular lines, because you want the inner rectangle to share two perpendicular sides of the outer rectangle. (It is actually easy to show you, but using words may be confusing). You label the left-over sides B and D.
What is the area of the inside rectangle? It is
(A - B)(C - D) = AC - AD - BC + BD
Let's look at the right hand side of the equation. The first term AC is the area of the outside rectangle. You subtract the rectangles AD and BC, but AD and BC overlap, you subtracted too much! You have to add back their intersection BD to find the area of the inner rectangle. Multiplying two negatives must then be equal to a positive.

Answer 5

Let me explain it like this:

Understand what multiplication means.

2 x 2 means two lots of twos and therefore equals 4.

3 x 2 means 3 lots of twos amd therefore equals 6

It follows that
-1 x 1 means one lot of -1 and therefore equals -1

So it follows if -1 x 1 = -1 then -1 x -1 has to be of opposite sign and therefore equals +1.

This is a crude but easy and logical to follow explanation.

Answer 6

because negative times positive is negative so -ve times -ve has to be the opposite of this

-1 * -1 = +1
-1 *(+1) = -1

Answer 7

bcoz if we do -2*-2 =4
two negative signs cancel out each others effect and so it bcomes +ve.

also it is a fact which can't be changed.. accept it like that..

Answer 8

Yea, just a math rule.

I never worked it out either.... but the good thing is that it's now in your mind. You'll never forget it now.

Answer 9

bcoz we plus neative and negative


y to ask y for every point.

ITS A FORMULA WHICH IS A BASIC STEP TO LEARN ABOUT INTEGERS.

Answer 10

That's just a fundamental law of mathematics. There's no explaining "why", it just "is".