Mathmatical Rules, multiplying two negative numbers.

[Mudster]

Yup, I pay a man to do my books, more so becasue as a Ltd company if my accounts are submitted by a Chartered Accountant I get left alone by HMRC and banks etc automatically accept them without question.

 

[Mozzer]

Try here :

YouTube - Math: Negative Times Negative Equals Positive

 

[lil.smartie]

I upset a maths teacher cos I needed to know 'why' on several occasions I was sent to the head of maths to try and get an answer (and get me out of his lesson!)

That was A-level, I'd had the Head Master as my maths teacher at my previous school (GCSE & AS-Level lessons) he knew a heck of a lot more than the idiot I got at College and didn't mind going off on a tangent when asked questions pretty sure we all learnt a lot from him!
My husband is a qualified maths teacher with a proper maths degree and his kids didn't stand a chance round here when they got maths homework lol

Kate

 

[Gollom]

The expalantions sound like Vogon poetry to me.......

Oh freddled gruntbuggly,
Thy micturations are to me
As plurdled gabbleblotchits
On a lurgid bee
That mordiously hath bitled out
Its earted jurtles
Into a rancid festering [drowned out by moaning and screaming]
Now the jurpling slayjid agrocrustles
Are slurping hagrilly up the axlegrurts
And living glupules frart and slipulate
Like jowling meated liverslime
Groop, I implore thee, my foonting turlingdromes
And hooptiously drangle me
With crinkly bindlewurdles,
Or else I shall rend thee in the gobberwarts with my blurglecruncheon
See if I don't.

 

[Mudster]

Oh freddled gruntbuggly,
Thy micturations are to me
As plurdled gabbleblotchits
On a lurgid bee
That mordiously hath bitled out
Its earted jurtles
Into a rancid festering [drowned out by moaning and screaming]
Now the jurpling slayjid agrocrustles
Are slurping hagrilly up the axlegrurts
And living glupules frart and slipulate
Like jowling meated liverslime
Groop, I implore thee, my foonting turlingdromes
And hooptiously drangle me
With crinkly bindlewurdles,
Or else I shall rend thee in the gobberwarts with my blurglecruncheon
See if I don't.

That makes more sense to me than -4 x -8 = +32

 

[crockers]

That makes more sense to me than -4 x -8 = +32

Seems a case of .......

 

[Benzowner]

Just accept as I did at school, its the rules and the reason you cannot have minus square roots

 

[wemorgan]

Just accept as I did at school, its the rules and the reason you cannot have minus square roots

oh dear, I wondered when this might appear

the answer is 'i'

but let's not go there

though if you do want to go there:
http://en.wikipedia.org/wiki/Imaginary_unit

 

[corned]

You'll be wanting to divide by zero next!

(Just ask Bill Gates and the US military (USS Yorktown) what happens when you do).

 

[Mozzer]

How about 2=1, just found this :

"You may have seen this little proof that 2=1:

a = x [true for some a's and x's]
a+a = a+x [add a to both sides]
2a = a+x [a+a = 2a]
2a-2x = a+x-2x [subtract 2x from both sides]
2(a-x) = a+x-2x [2a-2x = 2(a-x)]
2(a-x) = a-x [x-2x = -x]
2 = 1 [divide both sides by a-x]

But there is the mistake? Think about it.

All of the steps are perfectly legal except for the last one, dividing both sides by a-x. What is a-x? Well, a=x (step 1), so a-x=0. In the last step, we divided by zero. That's not allowed. And this puzzle is a good example of why it is not allowed, because if it were allowed, 2 would indeed equal 1."

Now I'm going to drink 1 beer (or is it 2 ?)

 

[NormanC]

Where it gets interesting is considering Factorials.

4! = 4 x 3 x 2 x 1
3! = 3 x 2 x 1
2! = 2 x 1

and so on but.....

0! = 1

This is because e ( the root of Natural Logarithms ) is defined as

1 / 0! + 1 / 1! + 1 / 2! + 1 / 3! + ........... + 1 / n!

and evaluates to 2.718281828. For this to be true then 0! = 1

Now that is mind blowing.

 

[johnsco]

1. one x 8 bananas is obviously plus 8 bananas

2. Minus one x 8 bananas is minus 8 bananas ('cos you've negated the quantity)

3. One x minus 8 bananas is clearly minus 8 bananas

4. From 2. above ... If you negate that statement, you get your plus 8 bananas back.
In other words you've multiplied your answer by minus 1 and negated the statement again.
You're back to where you started.

So that:
Minus 1 x minus 1 x plus 8 bananas = plus 8 bananas
Therefore minus 1 x minus 1 = plus 1.

The square root of minus 1 is easy, by comparison.

 

[Ted]

I work in binary and set the sign bit.
Then use twos complement.

Simples.

 

[Mudster]

1. one x 8 bananas is obviously plus 8 bananas

2. Minus one x 8 bananas is minus 8 bananas ('cos you've negated the quantity)

3. One x minus 8 bananas is clearly minus 8 bananas

4. From 2. above ... If you negate that statement, you get your plus 8 bananas back.
In other words you've multiplied your answer by minus 1 and negated the statement again.
You're back to where you started.

So that:
Minus 1 x minus 1 x plus 8 bananas = plus 8 bananas
Therefore minus 1 x minus 1 = plus 1.

The square root of minus 1 is easy, by comparison.

I preferred the Vogon Poetry, it still makes more sense than Bananas.

 

[oldcro]

According to my calculator -6 times -6 = 36.
But -6 times -6 times -6 = -216.
Then 6 times -6 = -36.

Whoever invented the Zero number has a lot to answer for.

 

[stevesey]

z-transforms anyone.

 

[renault12ts]

According to my calculator -6 times -6 = 36.
But -6 times -6 times -6 = -216.
Then 6 times -6 = -36.

Whoever invented the Zero number has a lot to answer for.

All correct because -6 x -6 (-6) = -6 x 36 = -216.

 

[st4]

Good god this thread is tedious....

 

[renault12ts]

You don't have to read it.

 

[NormanC]

Good god this thread is tedious....

... but intellectually stimulating !