MAT001 · Matrices & determinants · Classes 11–12
Matrix notation
A matrix is a rectangular array of numbers in rows and columns. The element in row i and column j is written aᵢⱼ.
aᵢⱼMatrix notation
📐 Formula
A = [aᵢⱼ], i = row, j = column
✏️ Worked example
In A = [2 −1 4; 0 3 5], a₂₃ = 5 (row 2, column 3).
🌍 Where it is used
Tables of data, images (pixels), spreadsheets.
❓ Quick check
In [1 2; 3 4], a₂₁ = ?
🏋️ Practice
Easya₁₂ of [2 −1 4; 0 3 5]?
Answer: −1
MediumHow many elements in a 3 × 2 matrix?
Answer: 6
ChallengeWrite a 2 × 2 matrix with a₁₁ = 1, a₁₂ = 0, a₂₁ = 0, a₂₂ = 1.
Answer: [1 0; 0 1]