Question

25. Real numbers: Addition and subtraction in the re

Answers

GPT-4o mini
It seems like you might be asking about addition and subtraction of real numbers. Here's a brief overview of the concepts:

### Real Numbers
Real numbers include all the rational and irrational numbers. Rational numbers are those that can be expressed as the quotient of two integers (like \(\frac{1}{2}\)), while irrational numbers cannot be expressed as a simple fraction (like \(\sqrt{2}\) or \(\pi\)).

### Addition of Real Numbers
1. **Commutative Property**: For any two real numbers \(a\) and \(b\):
\[
a + b = b + a
\]
2. **Associative Property**: For three real numbers \(a\), \(b\), and \(c\):
\[
(a + b) + c = a + (b + c)
\]
3. **Identity Element**: The identity element of addition is 0. For any real number \(a\):
\[
a + 0 = a
\]
4. **Inverse Element**: Each real number \(a\) has an additive inverse, which is \(-a\):
\[
a + (-a) = 0
\]

### Subtraction of Real Numbers
Subtraction can be thought of in terms of addition of negative numbers:
1. **Expression as Addition**: Subtracting a real number is equivalent to adding its additive inverse. For any two real numbers \(a\) and \(b\):
\[
a - b = a + (-b)
\]
2. **Properties**: The properties of addition (commutative, associative) can also be applied in understanding subtraction when represented in terms of addition.

### Examples
- **Addition**:
- \(3 + 5 = 8\)
- \(-4 + 2 = -2\)
- **Subtraction**:
- \(8 - 5 = 3\) (which can also be seen as \(8 + (-5) = 3\))
- \(-3 - 7 = -10\) (this can be seen as \(-3 + (-7) = -10\))

### Conclusion
Understanding the properties of real numbers in addition and subtraction is fundamental in mathematics. These operations not only apply to integers but extend to fractions, decimals, and irrational numbers, making them quite versatile. If you have specific questions or need examples, feel free to ask!