Matrices (introduction)
Rectangular array of numbers. Add element-wise; multiply by scalar element-wise.
An m×n matrix has m rows and n columns. Two matrices of the same size add element-wise. Scalar multiplication scales every element.
Worked examples
A 2×3 matrix has 2 rows and 3 columns.
2×A multiplies every entry by 2.
A + B requires A and B to have the same dimensions.
Frequently asked questions
Why matrices?
Compact way to represent linear systems and transformations. Foundation of linear algebra.
Square matrix?
n×n. Special properties: determinant, inverse (often).