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why does negative*negative=positive?

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Original post by p29
i dont understand :frown:


There are numerous ways to explain it, but if you don't understand the explanations then clearly there is something wrong in your understanding of the fundamental principles. Watch this video:
[video="youtube;rK4sXm_MPWo"]https://www.youtube.com/watch?v=rK4sXm_MPWo[/video]
(edited 7 years ago)
Reply 41
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Original post by candyaljamila
PS: This analogy will be more easily understood if you're familiar with vectors, but that's not necessary.

If we have two terms multiplied, "a" being the first term and "b" the second term.

So imagine that when "a" is positive, it is represented by the "Right" direction and when it's negative it's represented by the "Left" direction.

For term "b", when it's positive it leaves you in the same direction, and if it's negative it takes you to the opposite direction.

If the two terms are negative, that leaves us with an "a" located at the "left" and a "b" flipping it to the opposite direction which would be "Right" or "Positive".

what direcshion, north, east, south o west?
Reply 42
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Original post by RDKGames
There are numerous ways to explain it, but if you don't understand the explanations then clearly there is something wrong in your understanding of the fundamental principles. Watch this video:
[video="youtube;rK4sXm_MPWo"]https://www.youtube.com/watch?v=rK4sXm_MPWo[/video]


thx so much, but why do negative nnumbers exist? they r dumb
because if you multiply something by a negative, it *has* to go down and become more negative

...but in terms of negative numbers, "down" is actually up, because a lesser number is actually "more"
for instance, I'm going to take away 6 from -22. the answer is "larger", -16.
but it's a "smaller" number...while also a "larger" number in terms of the scale between negative numbers, 0, and positive numbers.

so (-6) (on the scale, lower than zero) multiplied (proportioned to...) by -6 (again, on the negative scale)
...is -36 because it's become proportioned to a *negative*, so it must go that way down the scale
(edited 7 years ago)
Original post by p29
thx so much, but why do negative nnumbers exist? they r dumb


You might as well ask why the universe exists.

And please don't call my babies dumb :frown:
Original post by p29
thx so much, but why do negative nnumbers exist? they r dumb


Because the number line is continuous as it has no start nor end. Negative numbers express quantities smaller than 0, just as positive number express quantities larger than 0. The number 0 is just a bit like a centre point of the number line as it goes to infinity in both directions.
(edited 7 years ago)
Original post by ValerieKR
Any complex number can be written in the form re^i(theta), for negative numbers theta = (2n+1)pi (r is the (positive) magnitude of the negative number)
When you multiply two numbers:
re^i(2n+1)pi*se^i(2m+1)pi = rse^i(2n+2m +2)pi = rse^i(2k)pi
e^ik(2pi) = 1
therefore = rs*1 = rs
no negative sign any more


loooooooooool
Imagine you're told to "face the opposite direction" twice.
You'll just end up facing the direction you were, originally.*
Original post by p29
what direcshion, north, east, south o west?


Right direction is east, and left direction is west.
Reply 49
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Original post by RDKGames
Because the number line is continuous as it has no start nor end. Negative numbers express quantities smaller than 0, just as positive number express quantities larger than 0. The number 0 is just a bit like a centre point of the number line as it goes to infinity in both directions.

0=nothing there is nothing smller than nothin. They should be band.
Original post by p29
0=nothing there is nothing smller than nothin. They should be band.


You should be band...

Spoiler

Original post by Productivity
This thread is painful to read.


I thought I was the only one!!!
Hopefully these experts will not become teachers!
Original post by p29
0=nothing there is nothing smller than nothin. They should be band.


A negative number has no meaning physically but it has much meaning when dealing with more abstract things like money in finance. Sometimes you may take out more money than you're allowed and the bank needs some number to record that, can't use a positive number for the balance otherwise you would still have something left whereas a negative number would indicate you need to insert some money back in rather than take it out, since you're now in debt.
(edited 7 years ago)
Reply 53
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Original post by ValerieKR
You should be band...

Spoiler



im sad :frown:
Original post by ODES_PDES
I thought I was the only one!!!
Hopefully these experts will not become teachers!


Not unless I plan on failing the next generation :colone:
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Original post by ODES_PDES
I thought I was the only one!!!
Hopefully these experts will not become teachers!

i still dont understand:frown: only this helped:
"Basically if you rotate one of the minus' by 90 degrees and add it on top of another minus it equals a plus"
:frown::frown:
(edited 7 years ago)
Original post by p29
i still dont understand:frown: only this helped
"Basically if you rotate one of the minus' by 90 degrees and add it on top of another minus it equals a plus"
:frown::frown:


lol just leave it, TSR isn't quite the best place to get primary school education explained
Reply 57
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Original post by RDKGames
lol just leave it, TSR isn't quite the best place to get primary school education explained

common sense?? my eyes,ears,nose and hands work.......
Reply 58
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helpi dont understand
Reply 59
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Original post by p29
yh

If you're happy with the following

−x(y+−y)≡0-x(y + -y) \equiv 0

and are happy with distributivity (expanding brackets) then:

−x(y+−y)≡−xy+(−x×−y)≡0-x(y + -y) \equiv -xy + \left(-x \times -y\right) \equiv 0


⇒−x×−y≡xy\Rightarrow -x \times -y \equiv xy


Intuitively, it can be hard to explain and many teachers don't try. This link has a few explanations.

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