Binary Operations and Their
Properties
An Introduction with Examples
What is a Binary Operation?
• A binary operation is a rule for combining two
elements (a and b) from a set to produce another
element from the same set.
• It is usually denoted as: a * b
Examples of binary operations:
• - Addition: a + b
• - Multiplication: a × b
• - Matrix multiplication (defined over matrices)
Properties of Binary Operations
• 1. **Closure**: If a and b are in set S, then a *
b is also in S.
• 2. **Commutativity**: a * b = b * a
• 3. **Associativity**: (a * b) * c = a * (b * c)
• 4. **Identity Element**: There exists e such
that a * e = a = e * a
• 5. **Inverse Element**: For every a, there
exists a' such that a * a' = e
Example 1: Addition on Integers (ℤ,
+)
• - Operation: a + b, where a, b ∈ ℤ
• - Closure: Always results in another integer
• - Commutative: a + b = b + a
• - Associative: (a + b) + c = a + (b + c)
• - Identity Element: 0 (a + 0 = a)
• - Inverse Element: For a, inverse is -a (a + (-a) =
0)
Example 2: Multiplication on Real
Numbers (ℝ, ×)
• - Operation: a × b, where a, b ∈ ℝ
• - Closure: Always results in another real
number
• - Commutative: a × b = b × a
• - Associative: (a × b) × c = a × (b × c)
• - Identity Element: 1 (a × 1 = a)
• - Inverse Element: For a ≠ 0, inverse is 1/a (a ×
1/a = 1)
Binary Operations and Their
Properties
An Introduction with Examples