Why does -1 x -1 = +1?

Original post by Kabulkid

*high five*

hows life? (im expecting an elaborate answer).. :tongue:

It's getting by.. slowly. Ramadan is going quick though. The weather is superb, so sunny and hot!! Although I'm really thirsty, another 5 hours to go. Time spent on TSR goes so fast like omgg! What upppp

Reply 22

cheeriosarenice

[QUOTE="QuantumDuckling;48695154"] x QUOTE]

Original post by james22

x

No, it doesn't make sense. If I don't have a burger, and my friend also doesn't have a burger, that doesn't make a burger

Reply 23

Original post by Afghan Warrior

It's getting by.. slowly. Ramadan is going quick though. The weather is superb, so sunny and hot!! Although I'm really thirsty, another 5 hours to go. Time spent on TSR goes so fast like omgg! What upppp

ah thats good to hear, yeah ramadhan is coming to an end :frown:

what country r u originally from and u doing a-levels/gcse?

im awaiting A2 results so nervy as hell.

Reply 24

Original post by Kabulkid

ah thats good to hear, yeah ramadhan is coming to an end :frown:

what country r u originally from and u doing a-levels/gcse?

im awaiting A2 results so nervy as hell.

Parents are born from Pakistan, I'm from here. Don't ask about my username, I'm tired of telling everyone the story behind it. I've just done AS levels, waiting for the results. Proper messed up though, gonna have to resit all the exams, if my sixth form don't kick me out.
Oh, well good luck!! What are you hoping to get?

Reply 25

Original post by Afghan Warrior

Parents are born from Pakistan, I'm from here. Don't ask about my username, I'm tired of telling everyone the story behind it. I've just done AS levels, waiting for the results. Proper messed up though, gonna have to resit all the exams, if my sixth form don't kick me out.
Oh, well good luck!! What are you hoping to get?

ahh hopefully your results go well for you, why did you mess up?

im hoping to get A*A*A but make dua please :smile:

i'll make dua as well.

Reply 26

Med_medine

1

Original post by Numberwang

Simply because multiplication means how many of the thing you have , for example

5x3 means you have 5 threes or 3 fives

Therefore -1 x -1 means you have negative one negative ones, aka a positive one
If you have a negative neg, you get a positive, the same law as having a positive positive, you get a positive.

I am not "not smart" means I am smart

This is from a student with 100% in all further math modules

Posted from TSR Mobile

Reply 27

miser

20

Aside from axiomatic, definitional explanations, it can be imagined that you have -1 amounts of -1.

Consider that we have 1 quantity of -1. In this case, we simply have -1.

Now consider that we have 0 quantities of that -1. Now we have 0, because we have no -1s. Notice that 0 is greater than the -1 we had originally.

Now we decrease the quantity of -1s we have even more, so that now we say that we have -1 quantities of -1. Now we have even fewer than 0 quantities of -1, so the number that results is again higher than before, and we have 1.

If we have -1 amounts of -1, that is just another way of saying that we have 1.

I'm not sure if other people's imaginations work the same as mine but this is how I imagine it.

Reply 28

Numberwang

OP

12

Original post by Med_medine

Simply because multiplication means how many of the thing you have , for example

5x3 means you have 5 threes or 3 fives

Therefore -1 x -1 means you have negative one negative ones, aka a positive one
If you have a negative neg, you get a positive, the same law as having a positive positive, you get a positive.

I am not "not smart" means I am smart

This is from a student with 100% in all further math modules

Posted from TSR Mobile

Best, easiest and most respectful explanation so far, thanks :smile:

I love using the double-negative for comic effect, so it's great you used it for comparison

Reply 29

QuantumDuckling

Original post by cheeriosarenice

No, it doesn't make sense. If I don't have a burger, and my friend also doesn't have a burger, that doesn't make a burger

But that analogy is about adding your amount of burgers, and the number of burgers you and your friend have is 0, not -1 :tongue:

Reply 30

Notnek

21

Original post by cheeriosarenice

No, it doesn't make sense. If I don't have a burger, and my friend also doesn't have a burger, that doesn't make a burger

That's addition : -1 + (-1) = -2

Multiplication:

You owe your friend a burger so you have -1 burgers. Your friend becomes a vegetarian (a negative operation) and lets you off the burger you owed him. Now you have 0 burgers so one has been added to your burger collection.

i.e. -1 x -1 = 1.

(edited 9 years ago)

Reply 31

Original post by Kabulkid

ahh hopefully your results go well for you, why did you mess up?

im hoping to get A*A*A but make dua please :smile:

i'll make dua as well.

I encountered some problems throughout the year, in fact ive had them for a few years now. During the year i understood everything but i found it hard to use my time effectively to make sure i dont forget the stuff. And of course with exam stress on top of the other stress it all just got too much to handle for me. Oh well. Everything happens for a reason.
Mashallah, you must be smart! What do you wanna study at uni? And I will :smile:

do dua for me too please, im really gonna need it!

Reply 32

Original post by Afghan Warrior

I encountered some problems throughout the year, in fact ive had them for a few years now. During the year i understood everything but i found it hard to use my time effectively to make sure i dont forget the stuff. And of course with exam stress on top of the other stress it all just got too much to handle for me. Oh well. Everything happens for a reason.
Mashallah, you must be smart! What do you wanna study at uni? And I will :smile:

do dua for me too please, im really gonna need it!

so sorry to hear that, yeah everything happens for a reason, it's all written so don't worry!

thank you haha, inshaAllah i study engineering @ either cambridge or imperial, depending on what I get. :smile:

Reply 33

james22

16

Original post by cheeriosarenice

No, it doesn't make sense. If I don't have a burger, and my friend also doesn't have a burger, that doesn't make a burger

What's the flaw in my reasoning then?

Reply 34

Original post by Kabulkid

so sorry to hear that, yeah everything happens for a reason, it's all written so don't worry!

thank you haha, inshaAllah i study engineering @ either cambridge or imperial, depending on what I get. :smile:

Check you out, engineering ey :P what kinda engineering?

Reply 35

scrotgrot

16

Original post by Numberwang

Plot a square -1 by -1 and measure the area.

Geometry is the key to visualising many non-natural numbers.

Reply 36

cheeriosarenice

Original post by james22

What's the flaw in my reasoning then?

You didn't orde any fries

Reply 37

Original post by Afghan Warrior

Check you out, engineering ey :P what kinda engineering?

haha thanks :wink:

cambridge's course is general engineering and imperial is civil engineering, either one would be amazing tbh but still, cambridge is cambridge :tongue:

Reply 38

james22

16

Original post by scrotgrot

Plot a square -1 by -1 and measure the area.

Geometry is the key to visualising many non-natural numbers.

Doesn't work, plot a 1*-1 square and measure the area.

Reply 39