| ( | 5 | − | 2 | x | ) | ( | 4 | − | 2 | x | ) | = | 0 |
| Left side of the equation = | 5 | ( | 4 | − | 2 | x | ) | − | 2 | x | ( | 4 | − | 2 | x | ) |
| = | 5 | × | 4 | − | 5 | × | 2 | x | − | 2 | x | ( | 4 | − | 2 | x | ) |
| = | 20 | − | 10 | x | − | 2 | x | ( | 4 | − | 2 | x | ) |
| = | 20 | − | 10 | x | − | 2 | x | × | 4 | + | 2 | x | × | 2 | x |
| = | 20 | − | 10 | x | − | 8 | x | + | 4 | x | x |
| = | 20 | − | 18 | x | + | 4 | x | x |
| 20 | − | 18 | x | + | 4 | x | x | = | 0 |
| x2= | 5 2 |