You are Here: Home

# why does negative*negative=positive Watch

1. why does negative*negative=positive
2. "+"=2 lines
"-"=1 line
"-"+"-"=1 line + 1 line = 2 lines = "+"
3. (Original post by DanArthur)
"+"=2 lines
"-"=1 line
"-"+"-"=1 line + 1 line = 2 lines = "+"
lmao
4. You know, negative numbers were not widely accepted until the 18h century. Even then, they were contentious in some circles.

I dont know it but ill bet money that the explanation for this is something really obscure and complicated which probably involves complex numbers and trigonometry as well because thats just the way maths works.
5. (Original post by DanArthur)
"+"=2 lines
"-"=1 line
"-"+"-"=1 line + 1 line = 2 lines = "+"
This is probably the most logical explanation of that mathematical rule I have ever seen
6. 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=
we know e^ik(2pi) = 1
therefore = rs*1 = rs
no negative sign any more (as r and s are both magnitudes (not 0 as we specified the original number is negative) and therefore positive).
7. Just imagine 1 dimension where negative is the reverse direction from zero, so by timesing you get --1 which is essentially reverse reverse 1
which would be 1.
8. (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
This makes my brain hurt. You're smart!
9. fml

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 29, 2016
Today on TSR

### Last-minute PS help

100s of personal statements examples here

### Loneliness at uni

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
Bizarre things students have spent their loans onThings you should budget for at uni

### Need some cash?

How to make money running your own website.

What would an employer find out about you on Google? Find out how to take control.

## 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.