Linear Algebra · Lesson 3
Matrices – Intro & Addition
A matrix is a rectangular array of numbers arranged in rows and columns. Matrices are the workhorses of linear algebra — they represent systems of equations, transformations, data tables, and graphs all in one structure.
Quick Check
1. A 3×4 matrix has how many entries?
7
12
3
16
2. Matrix addition requires the matrices to have:
Square dimensions
The same dimensions
The same entries
Nonzero determinant
3. If A = [[2, 4], [6, 8]], what is 3A?
[[5,7],[9,11]]
[[6,12],[18,24]]
[[2,4],[6,8]]
[[6,7],[8,9]]
4. The transpose of a 2×3 matrix is:
2×3
3×2
2×2
3×3