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Maths Exercices

A matrix is a rectangular table of elements (usually called entries), which may be numbers.. We are only going to work with matrices which entries are real numbers.

The horizontal lines in a matrix are called rows and the vertical lines are called columns. A matrix with m rows and n columns is called an m-by-n matrix (written m × n) and m and n are called its dimensions.

(Frecuently an m-by-n matrix is said to has an order of m × n ("order" = "size")).

A 3x3 matrix can be:

While a general mxn matrix is:

that can be written as: A = (aij ), where i=1,...,n and j=1,2,...,m

Observe that almost always upper-case letters denote matrices, while the corresponding lower-case letters, with two subscript indices, represent the entries, for example, the (i,j)th entry of a matrix A is most commonly written as ai,j.