| ( | 1 | − | x | ) | ( | 1 | − | x | − | 3 10 | ) | = | 3 20 |
| Left side of the equation = | 1 | ( | 1 | − | x | − | 3 10 | ) | − | x | ( | 1 | − | x | − | 3 10 | ) |
| = | 1 | × | 1 | − | 1 | x | − | 1 | × | 3 10 | − | x | ( | 1 | − | x | − | 3 10 | ) |
| = | 1 | − | 1 | x | − | 3 10 | − | x | ( | 1 | − | x | − | 3 10 | ) |
| = | 7 10 | − | 1 | x | − | x | ( | 1 | − | x | − | 3 10 | ) |
| = | 7 10 | − | 1 | x | − | x | × | 1 | + | x | x | + | x | × | 3 10 |
| = | 7 10 | − | 17 10 | x | + | x | x |
7 10 | − | 17 10 | x | + | x | x | = | 3 20 |