/sci/ - Science & Math

[Anonymous No.3118611]

hey guys i just got an idea if we multiply 2 electrons together do we get a proton?

alright serious question though about the timecube thread posted here earlier.

Is there any mathematical prove for -1*-1=1 how come that 1*1=1 not -1 why do the negatives cancel out when multiplied together?

what is the nature of multiplication of negatives?
i get that if you have 3 pen sets and each set contains 5 pens then you have 15 pens but if you have -3 pen sets with -5 pens you also have 15 pens?

same goes for division of obviously. i am just wondering is it a mathematical convention. What does multiplication of negatives actually mean.

[Anonymous No.3118614]

ITT: Arithmetic 101
+ + = +
- - = +
+ - = -
- + = -

[Anonymous No.3118637]

>>3118614
i know that but that is not the question. the question is why is -1*-1=1 but the converse of 1*1=-1 is not true.

inb4 no one can explain why -1*-1=1

[Anonymous No.3118643]

(-x)(y)+(-x)(-y)=(-x)(y-y)=(-x)(0)=0
as (-x)(y)=-xy
then (-x)(-y)-xy=0
so (-x)(-y)=xy

[Anonymous No.3118644]

>>3118637
Obviously you don't, you trolling faggot.

[Anonymous No.3118657]

Er, is this a troll post?

A good way to think about this is multiplication by negative one will "flip" the number-line; it scales everything by 1, and flips. So -1 will be scaled by 1 and flipped to 1. Hence -1 * -1 = 1. For a proof...

(1 + (-1)) = 0
-1(1 + (-1)) = -1(0) = 0
-1*1 + -1(-1) = 0
-1 + -1(-1) = 0
1 + (-1) + -1(-1) = 1 + 0
0 + -1(-1) = 1
-1(-1) = 1.

[Anonymous No.3118662]

>>3118611
No, two electrons multiplied together result in a homotron. It is the particle responsible for blowing fuses.

[Anonymous No.3118670]

we had such a thread months ago and in the end it was about 200 posts long.

In the end it has to do with the fact that you're dealing with a ring
http://en.wikipedia.org/wiki/Ring_theory
(check the formal definition)

you have two operations * and +, and + has an inverse -, such that
a+(-a)=0.
by multiplying with (-a) you get
a*(-a)+(-a)*(-a)=0
or
(-a)*(a)+(-a)*(-a)=0
or
-(a*a)+(-a)*(-a)=0
adding a*a on both sides you get
(-a)*(-a)=a*a.

the main step omitted is why for example

(-a)*b*c*···*x*y*z) = a*b*c*···*x*(-y)*z

or simpler why
(-3)*5 = 3*(-5)
etc

which is due to

additive_inverse[a*b]
=a*additive_inverse[b]
=additive_inverse[a]*b

which is a property of at least every abelian/commutative group

http://en.wikipedia.org/wiki/Abelian_group

(and the + symbol of the ring denotes that this operation is an additive group.)

You could/should think of muliplying by -1 as an operation, like a reflection in a mirror.
then the term (-1)*(-1), which is part of
>but if you have -3 pen sets with -5 pens you also have 15 pens?
is two times this operation and a reflection of a reflection is no reflection.

this analogy or 'multiplying a negative number with a negative number' and 'doning two reflections' works because both are involutions

http://en.wikipedia.org/wiki/Involution_%28mathematics%29

another example for an involution would be the complex conjugation:

(z*)*=z
http://en.wikipedia.org/wiki/Complex_conjugation
or the hodge star operation
http://en.wikipedia.org/wiki/Hodge_star

[Anonymous No.3118671]

I've always imagined it like this:

If you add something negative, the result is negative.
If you add something positive, the result is positive.
If you remove something positive, the result is negative.
If you remove something negative, the result is positive.

As for the fact that negative cancels negative, but not the other way around, I try to think of it in the way of to equal signs producing something positive.

I.e. two charged particles don't care which signs their charges have. They only need to know if they have the same charge or not.

For the negative collection of negative pens, however, I can not find a suiting analogy.

[Anonymous No.3118678]

Hey guise, what if two black holes of equal mass collide?

Anyone else see that thread on /b/ last night?

[Anonymous No.3118719]

I find it absolutely incredible people have problems with basic stuff like this.

It's such a shame how school teaching ruins mathematics.

[Anonymous No.3118734]

Assume that -1*-1= -1 and sooner or later you will arrive at a contradiction.

Here is an example:

-1(10-8)=-1(2) =-2

Right?

But if -1*-1=-1

-1(10-8)=(-10-8)=-18

That's incoorect.

[Anonymous No.3118784]

>>3118670
>>3118657
>>3118670


alright OP here, i get it now.

yes the electron proton thing was just a troll but i was genuinely confused about why two negatives multiplied together was positive. It is not that i didn't know the fact it is just that in school they teach you -x*-x=x^2 and never why this actually happens.

[Anonymous No.3118856]

>>3118784
> i was genuinely confused about why two negatives multiplied together was positive

This is so fucking sad

I'm not getting at you, I think the whole education system actively works against teaching people, and the mathematics curriculum is completely wrong

> that feel when I know how to improve it but would never be able to have any influence

[Anonymous No.3118899]

>>3118662

[sage No.3119099]

you can think of it as a normal x,y plane

if you draw a rectangle starting at the origin that only stays in the third quadrant, you'd have the problem you're talking about.

The problem here is your conceptualization of the negative sign. Most quantities in life are actually constrained to be positive (EX: negative pens has no meaning). But, for those things that have meaning, the result is intuitive.

EX: lets say you're standing at a point. You decide to build a fence -5 feet to your right and -5 feet forward. Your fence will enclose 25 square feet. It's just that those 25 feet are actually to your left and back.

hope it helped

[Anonymous No.3119232]

>>3118856
be strong fellow US citizen, the world is with you, good luck out there