| ( | 1 | − | a | ) | × | 3 | + | 4 | ( | 1 | + | 2 | a | ) | ( | 1 | − | a | ) | = | 7 |
| Left side of the equation = | 1 | × | 3 | − | a | × | 3 | + | 4 | ( | 1 | + | 2 | a | ) | ( | 1 | − | a | ) |
| = | 3 | − | a | × | 3 | + | 4 | ( | 1 | + | 2 | a | ) | ( | 1 | − | a | ) |
| = | 3 | − | 3 | a | + | 4 | × | 1 | ( | 1 | − | a | ) | + | 4 | × | 2 | a | ( | 1 | − | a | ) |
| = | 3 | − | 3 | a | + | 4 | ( | 1 | − | a | ) | + | 8 | a | ( | 1 | − | a | ) |
| = | 3 | − | 3 | a | + | 4 | × | 1 | − | 4 | a | + | 8 | a | ( | 1 | − | a | ) |
| = | 3 | − | 3 | a | + | 4 | − | 4 | a | + | 8 | a | ( | 1 | − | a | ) |
| = | 7 | − | 7 | a | + | 8 | a | ( | 1 | − | a | ) |
| = | 7 | − | 7 | a | + | 8 | a | × | 1 | − | 8 | a | a |
| = | 7 | − | 7 | a | + | 8 | a | − | 8 | a | a |
| = | 7 | + | 1 | a | − | 8 | a | a |
| 7 | + | 1 | a | − | 8 | a | a | = | 7 |
| a2= | 1 8 |