| ( | a | + | 1 | ) | ( | 10 | − | a | + | 4 | ) | = | 25 |
| Left side of the equation = | a | ( | 10 | − | a | + | 4 | ) | + | 1 | ( | 10 | − | a | + | 4 | ) |
| = | a | × | 10 | − | a | a | + | a | × | 4 | + | 1 | ( | 10 | − | a | + | 4 | ) |
| = | 14 | a | − | a | a | + | 1 | ( | 10 | − | a | + | 4 | ) |
| = | 14 | a | − | a | a | + | 1 | × | 10 | − | 1 | a | + | 1 | × | 4 |
| = | 14 | a | − | a | a | + | 10 | − | 1 | a | + | 4 |
| = | 13 | a | − | a | a | + | 14 |
| 13 | a | − | a | a | + | 14 | = | 25 |