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Okay this question seriously bugs me and i cant believe that i havent thought to ask on here.

Ive asked at school but not got a v good answer, my teacher basically said because it is and i just have to accept it.

So anyone know???

Ive asked at school but not got a v good answer, my teacher basically said because it is and i just have to accept it.

So anyone know???

rachelrainbow32

Okay this question seriously bugs me and i cant believe that i havent thought to ask on here.

Ive asked at school but not got a v good answer, my teacher basically said because it is and i just have to accept it.

So anyone know???

Ive asked at school but not got a v good answer, my teacher basically said because it is and i just have to accept it.

So anyone know???

Study the pattern.

steve2005

Study the pattern.

Similarly things like "They cancel out" don't have any rigour.

The proper way to show minus times a minus is a plus is the way C4>O7 has done it, by using the axiomatic approach. Once you've defined how 0 and 1 behave, the concept of additive inverses and the fact multiplication is distributive over addition you can show -1*-1 = 1.

yea but its like saying u have -1 orange and u had -2 oranges to get an orange?

ledzep15

- X - = + because if you multiply -1 x -1 you get 1!

asadtamimi

yea but its like saying u have -1 orange and u had -2 oranges to get an orange?

you can't have a negative number of oranges. similarly you can't have a fractional number of oranges. we can make use of these numners however to help us solve other problems.

people in my classes are having this problem now with complex numbers - they can't comprehend them since they can't immediately see their uses. it's good the thread starter is actually asking questions about the nature of numbers here, instead of just blindly accepting them.

spy007

-2 x -2 is -2 "lots" of -2 = -(-2-2) = 4

As I said, with these handwavey arguments you almost always end up using your assumption to prove the assumption. C4>07 proved it properly, algebraically using only basic axioms without any handwaving.

Positive and negative are relative. If you have two oranges and give one to your friend, the orange which you give away becomes negative, but only from your frame of reference. To your friend, the orange becomes positive, from negative.

When dealing with real numbers only we're dealing with a 1-dimensional space. Think of the multiplication of a negative as a rotation of through 180 degrees. Ie. if you multiply something by two negatives it will rotate a whole revolution through 360 degrees and end up with the same polarity you started with (if it was originaly negative it will still be negative, and likewise for positive).

When dealing with complex numbers we're dealing with a 2-dimensional space. The same concept can be applied, whereby multiplying by j (sqrt-1) will make a rotation through 90 degrees. So how about if we multiply by -j... the negative causes a rotation of 180 and j causes a rotation of 90... making a total rotation of 270 degrees.

By no means a proof, but its a lovely concept.

When dealing with real numbers only we're dealing with a 1-dimensional space. Think of the multiplication of a negative as a rotation of through 180 degrees. Ie. if you multiply something by two negatives it will rotate a whole revolution through 360 degrees and end up with the same polarity you started with (if it was originaly negative it will still be negative, and likewise for positive).

When dealing with complex numbers we're dealing with a 2-dimensional space. The same concept can be applied, whereby multiplying by j (sqrt-1) will make a rotation through 90 degrees. So how about if we multiply by -j... the negative causes a rotation of 180 and j causes a rotation of 90... making a total rotation of 270 degrees.

By no means a proof, but its a lovely concept.

Who said that two wrongs don't make a right, they're having a laugh!

The only way I could remember that, is that if the signs are different, the answer will be negative; if the signs are the same, the answer will be positive.

Wippa )

Wippa )

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