Is there a proof od negative numbers?

In summary, the conversation discusses the proof of negative numbers and why two negatives multiplied produce a positive. The proof involves showing that ab = (-a)(-b) using the identity property of multiplication and the concept of absolute value. The conversation ends with the conclusion that the only possible choices are (-1)(-1) = 1 or (-1)(-1) = -1.
  • #1
Geekchick
77
0
Hi everyone!

This may be a stupid question but is there a proof of negative numbers? Specifically why does this work -a(-b)=c I was trying to explain it to someone and drew a blank.

Thanks!
 
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  • #2
Are you asking why two negatives multiplied produces a positive? If so, here's a proof I once read:


Let x = ab + (-a)(b) + (-a)(-b)


Then, x = ab + -a(b-b)
= ab -a(0)
= ab - 0
= ab

However, we also have x = b(a -a) + (-a)(-b)
= (-a)(-b)

Therefore, ab = (-a)(-b). QED.

Hope that's what you wanted.
 
  • #3
Thanks i just couldn't logically reason it!
 
  • #4
1 is the identity and -1 can only change the sign. Since (-1) ab = -ab. Thus the absolute value of (-1)(-1) = 1. So we have only the choices (-1)(-1) = 1 or
(-1)(-1) = -1.
 

FAQ: Is there a proof od negative numbers?

What are negative numbers?

Negative numbers are a type of real number that is less than zero. They are represented by a "-" symbol in front of the number. Examples of negative numbers include -1, -5, and -0.25.

How do we know that negative numbers exist?

Negative numbers were first introduced as a concept in mathematics to solve equations that did not have a solution in the set of positive numbers. They were later proven to exist through the use of number lines and algebraic equations.

What is the proof of negative numbers?

The proof of negative numbers lies in the fundamental properties of arithmetic, such as the commutative, associative, and distributive properties. These properties hold true for negative numbers, just like they do for positive numbers. Additionally, the existence of negative numbers can also be proven through mathematical induction and the use of complex numbers.

Are there any real-world applications of negative numbers?

Yes, negative numbers have many real-world applications, such as in finance, where they represent debt or losses. They are also used in weather forecasting to represent temperatures below zero, and in physics to represent quantities such as velocity and acceleration in the opposite direction.

Can you multiply two negative numbers together?

Yes, two negative numbers can be multiplied together. The product of two negative numbers is a positive number. For example, (-2) x (-3) = 6. This can be understood through the concept of multiplication as repeated addition, where the negative signs cancel out and result in a positive number.

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