Example of zero divisors
In a commutative ring R R R with identity , a zero divisor is a nonzero element a ∈ R a \in R a ∈ R such that there exists a nonzero element b ∈ R b \in R b ∈ R with: a ⋅ b = 0 a \cdot b = 0 a ⋅ b = 0 Example 1: Integers Modulo 6 Consider the ring Z / 6 Z = { 0 , 1 , 2 , 3 , 4 , 5 } \mathbb{Z}/6\mathbb{Z} = \{0,1,2,3,4,5\} Z /6 Z = { 0 , 1 , 2 , 3 , 4 , 5 } under multiplication mod 6. 2 × 3 = 6 ≡ 0 m o d 6 2 \times 3 = 6 \equiv 0 \mod 6 2 × 3 = 6 ≡ 0 mod 6 Thus, 2 2 2 and 3 3 3 are zero divisors in Z / 6 Z \mathbb{Z}/6\mathbb{Z} Z /6 Z . Example 2: 2 × 2 2 \times 2 2 × 2 Matrices In the ring of 2 × 2 2 \times 2 2 × 2 matrices over R \mathbb{R} R , consider: A = [ 1 0 0 0 ] , B = [ 0 0 1 0 ] A = \begin{bmatrix} 1 & 0 \\ 0 & 0 \end{bmatrix}, \quad B = \begin{bmatrix} 0 & 0 \\ 1 & 0 \end{bmatrix} A = [ 1 0 0 0 ] , B = [ 0 1 0 0 ] Then: A B = [ 1 0 0 0 ] [ 0 0 1 0 ] = [ 0 0 0 0 ] A B = \begin{bmatrix} 1 & 0 \\ 0 & 0 \end{bmatri...