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What is infinity minus infinity?

Published in Mathematical Concepts 2 mins read

The answer to "infinity minus infinity" is undefined.

Understanding Infinity and Subtraction

When dealing with numbers, subtraction is straightforward. For example, 5 minus 2 equals 3. However, infinity is not a standard number; it is a concept representing something without any bound or limit. Therefore, basic mathematical operations do not apply the same way.

Why Infinity Minus Infinity is Undefined

The problem arises because infinity is not a specific value that we can accurately measure or calculate. As stated in a reference, "Mathematically, when two infinities are subtracted from each other, the answer is undefined. This is because infinity cannot accurately be measured and, therefore, cannot be added or subtracted from one another." (27-Dec-2022)

Here's a breakdown:

  • Infinity is Not a Number: Infinity (∞) signifies an endless quantity or an unbounded concept. It's not a number we can put on a number line and use in typical arithmetic operations.
  • Different "Sizes" of Infinity: There are different kinds of infinities, which are different "sizes". For example, the infinity of whole numbers is different from the infinity of real numbers. These different sizes contribute to why subtracting infinities isn't straightforward.
  • Undefined Result: If you try to subtract one infinity from another, you're not subtracting concrete values, but rather attempting to compare unbounded concepts. Depending on the situation, the result could be zero, a finite number, or another infinity. Since the answer cannot be determined universally, it is deemed undefined.

Analogy

Think of it this way: if you have two never-ending lines and try to compare their lengths, the difference is also never-ending and could be anything depending on the length of the lines. It's impossible to determine what one infinite line is if subtracted by another.

Conclusion

Concept Explanation
Infinity (∞) Represents something limitless, not a specific number.
Subtraction A defined mathematical operation for numbers, not for infinities.
Infinity - Infinity An undefined operation since the magnitude of infinities vary.

Therefore, the answer to the question "What is infinity minus infinity?" is undefined due to the nature of infinity.

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