Discrete Mathematics and Combinatorics

Appendix C

Matrices

Informally, a matrix is a rectangular array of numbers such as

 

 

Every horizontal sequence of numbers in the matrix is known as a row, and every vertical sequence of the matrix is known as a column. For example, (2.5 7 7) is a row of the third matrix above and is a column of the first matrix. Let us note that the second matrix has two rows and three columns. It is an example of 2×3 matrix. An m × n matrix is a rectangular array of numbers with m rows and n columns. The entry in the ith row and the jth column is denoted by ...