# 9.4 Matrix Operations

Add, subtract, and multiply matrices when possible.

Write a matrix equation equivalent to a system of equations.

In addition to solving systems of equations, matrices are useful in many other types of applications. In this section, we study matrices and some of their properties.

A capital letter is generally used to name a matrix, and lower-case letters with double subscripts generally denote its entries. For example, ${a}_{47}$, read “*a* sub four seven,” indicates the entry in the fourth row and the seventh column. A general term is represented by ${a}_{ij}$. The notation ${a}_{ij}$ indicates the entry in row `i` and column `j`. In general, we can write a matrix as

The matrix ...

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