# Key Concepts & Glossary

## Key Concepts

- An augmented matrix is one that contains the coefficients and constants of a system of equations.
- A matrix augmented with the constant column can be represented as the original system of equations.
- Row operations include multiplying a row by a constant, adding one row to another row, and interchanging rows.
- We can use Gaussian elimination to solve a system of equations.
- Row operations are performed on matrices to obtain row-echelon form.
- To solve a system of equations, write it in augmented matrix form. Perform row operations to obtain row-echelon form. Back-substitute to find the solutions.
- A calculator can be used to solve systems of equations using matrices.
- Many real-world problems can be solved using augmented matrices.

## Glossary

- augmented matrix
- a coefficient matrix adjoined with the constant column separated by a vertical line within the matrix brackets

- coefficient matrix
- a matrix that contains only the coefficients from a system of equations

- Gaussian elimination
- using elementary row operations to obtain a matrix in row-echelon form

- main diagonal
- entries from the upper left corner diagonally to the lower right corner of a square matrix

- row-echelon form
- after performing row operations, the matrix form that contains ones down the main diagonal and zeros at every space below the diagonal

- row-equivalent
- two matrices $A$and$B$are row-equivalent if one can be obtained from the other by performing basic row operations

- row operations
- adding one row to another row, multiplying a row by a constant, interchanging rows, and so on, with the goal of achieving row-echelon form

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