- X - = + Why?

[Enescu]

Why do 2 negative's = + ?

[wizzkid67]

b-b=0

multiply both sides by -a

(-a)*(b-B)=(-a)*0

 

(-a)*(b-B)=0

 

using the distributive axiom you get

(-a)*b+(-a)*(-B)=0

(-a)*b can be written as -(a*B)

 

can be written as -(a*B)+(-a)*(-B)=0

 

in order to get zero from -(a*B) u can use its additive inverse so (-a)*(-B) is just a*b in disguise

 

 

so (-a)*(-B)=a*b

 

that is a proof why two negtives = a postive

 

there is a simperler way lets assume that 2 negtives = a negative

 

x=-1

multiply by -1 so it become

-x=-1

-1 can not equal x and -x so the first thing we said must have been wrong two negtives must equal a postive

[Enescu]

That's the mathematical proof,

Nice explanation.

But that was not my question.

 

-a-b=-(a+B)

in day by day life we can say

I own you 6$ and you borrow me 2$ I now ow you 8$

-6-2=-8

 

now for the 2 negatives = positif

CAn you explain me why in a day by day exemple..

[wizzkid67]

so you are in debt right say u owe £6 if i take away £2 of that debt say 3 times its like saying

-2*-3 giving me £6 bring my debt to 0 i think that works its very diffecult trying to put negtive numbers in to everyday life

[Enescu]

again it works mathematicaly...but it dosent make any sense...- X + = - this can be easily explained

I owe you 3$ and i know owe you 3 times more

-3X3=-9

This makes sense

But the - - its hard to get around it in real life exemple's

 

You think you can come up with another exemple...B)

[Edge]

What about this example:

 

I owe $5 to someone. Then I borrow another $4 from that person. So, my money is:

 

-($5 + $4) = -$9

[Pyrotex]

so you are in debt right say u owe £6 if i take away £2 of that debt say 3 times its like saying

-2*-3 giving me £6 bring my debt to 0 i think that works its very diffecult trying to put negtive numbers in to everyday life

 

 

Hmmm...

it seems you are trying to understand -x- by

constructing arguments based on -+-.

 

Try this: we will say that receiving a 'chit' is a positive action (+). Giving someone a 'chit' is a negative action (-). IOW, giving someone a chit is the opposite or negative of receiving a 'chit' from them. The more chits you receive, the more chits you have! The more chits you give away, the fewer chits you have!

 

A chit is a monetary marker; it comes in two flavors. It may be positive (a $5 bill) or it may be negative (UOme $5). [i started by using IOU's but they don't work the opposite or negative of a positive chit. UOme's do.]

 

Okay?

Now you receive a $5 bill from each of 3 people.

(+3 x +$5) = +$15. You are richer!

 

Now you give a $5 bill to each of 3 people.

(-3 x +$5) = -$15. You are poorer!

 

Now you receive a $5 UOme from each of 3 people.

(+3 x -$5) = -$15. You are poorer!

 

Now you give a $5 UOme to each of 3 people.

(-3 x -$5) = +$15. You are richer!

[wizzkid67]

the last post seen was what i was trying to get across i found a website which explains it in a different way have a read

http://www.math.toronto.edu/mathnet/questionCorner/minustimesaminus.html

read this comment

Followup Comment by Buzz Breedlove on May 9, 1997:

[Enescu]

ok thx that link about the invers of a number gives a good enough explanation B)

[Edge]

This also applies to the real world. Example:

 

Two wrongs make a right.

 

B)

[Pyrotex]

This also applies to the real world. Example:

Two wrongs make a right.

 

Cute but relevant story ---

A pompous visiting professor from a stuffy British university was lecturing an English composition class in America. On the subject of syntax, he expressed contempt for the American habit of using double negatives to express a positive. He reasoned, "after all, you can't express a negative using a double positive, can you?!"

An American graduate student on the front row said just loudly enough to be heard throughout the room, "Yeah! Right!"

[learnin to learn]

Cute but relevant story ---

A pompous visiting professor from a stuffy British university was lecturing an English composition class in America. On the subject of syntax, he expressed contempt for the American habit of using double negatives to express a positive. He reasoned, "after all, you can't express a negative using a double positive, can you?!"

An American graduate student on the front row said just loudly enough to be heard throughout the room, "Yeah! Right!"

 

lol that is awsome!!!

 

EdgeThis also applies to the real world. Example:

 

Two wrongs make a right.

 

:hihi:Yesterday 10:17 PM

lol or is it 2 rights make a wrong????

[kamil]

That's the mathematical proof,

Nice explanation.

But that was not my question.

 

-a-b=-(a+:confused:

in day by day life we can say

I own you 6$ and you borrow me 2$ I now ow you 8$

-6-2=-8

 

now for the 2 negatives = positif

CAn you explain me why in a day by day exemple..

 

lets say 1.) -a=b ,then 2.) -b=a

multiple both sides by -

3.) -(-B)=-a

substitute equation 1.) to equation 3.)

-(-B)=b

 

for the more visual example: Lets say there are two opposite directions labeled - and +. If I walk towards the negative of the + i am walking towards the negative, but if i am facing the - and am moving in the direction which would be negative to me i am then moving to what was originally stated as '+'. Just like if i am facing backwards and moving backwards i am moving forwards. Imagine that on a number line.