A matrix is a grid of entries in row/column format. Matrix entries are denoted by a
ij where is the row and j is the column
| a11 | a12 | a13 |
| a21 | a22 | a23 |
| a31 | a32 | a33 |
Matrix addition and subtraction involves adding or subtracting respective matrix entries
| a11 | a12 | a13 |
| a21 | a22 | a23 |
| a31 | a32 | a33 |
| b11 | b12 | b13 |
| b21 | b22 | b23 |
| b31 | b32 | b33 |
| a11 + b11 | a12 + b12 | a13 + b13 |
| a21 + b21 | a22 + b22 | a23 + b23 |
| a31 + b31 | a32 + b32 | a33 + b33 |