You are Here: Home >< Maths

# why does negative*negative=positive? Watch

1. Basically if you rotate one of the minus' by 90 degrees and add it on top of another minus it equals a plus

- - = +

Posted from TSR Mobile
2. (Original post by shohaib712)
Basically if you rotate one of the minus' by 90 degrees and add it on top of another minus it equals a plus

- - = +

Posted from TSR Mobile
ok
3. (Original post by p29)
ok
The 90 comes from space.
4. (Original post by ValerieKR)
The 90 comes from space.
wow
6. (Original post by Productivity)
y
7. (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
Thanks for clearing that up... lol jk thanks for taking time to explain just a little lost hehe
9. (Original post by Bernie2016)
Thanks for clearing that up... lol jk thanks for taking time to explain just a little lost hehe
Easiest proof you'll find http://www.school-for-champions.com/...m#.V8NsBmjRYwg
10. (Original post by p29)
yh
Ask the insanely brainy person who came up with this rule because I sure as hell don't understand it.
11. Because God demands it to be so. Don't question it.
12. What are your starting axioms?
13. (Original post by RDKGames)
Because God demands it to be so. Don't question it.
y

http://www.confused.com
14. (Original post by Zacken)
idk i think its (2,1) (5,7)
15. (Original post by HamzahPatel)
Ask the insanely brainy person who came up with this rule because I sure as hell don't understand it.
where????
16. How dare you question God! You and the non-believers will burn eternally in the sulphurous pit with Satan the AntiChrist and the False Prophet!
Unless you pray to this arab dude with white skin and blue eyes - then you'll instead go to utopia.
17. (Original post by ValerieKR)
How dare you question God! You and the non-believers will burn eternally in the sulphurous pit with Satan the AntiChrist and the False Prophet!
Unless you pray to this arab dude with white skin and blue eyes - then you'll instead go to utopia.
18. Do you genuinely not understand why that is?
19. (Original post by RDKGames)
Do you genuinely not understand why that is?
i dont understand
20. (Original post by p29)
yh
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".

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: August 30, 2016
Today on TSR

### Am I pregnant?

...or just paranoid?

### Have I ruined my eyebrows

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.