| ( | 6 | x | − | 7 | ) | ( | x | − | 7 | ) | ( | 9 | x | + | 1 | ) | = | 0 |
| Left side of the equation = | 6 | x | ( | x | − | 7 | ) | ( | 9 | x | + | 1 | ) | − | 7 | ( | x | − | 7 | ) | ( | 9 | x | + | 1 | ) |
| = | 6 | x | x | ( | 9 | x | + | 1 | ) | − | 6 | x | × | 7 | ( | 9 | x | + | 1 | ) | − | 7 | ( | x | − | 7 | ) | ( | 9 | x | + | 1 | ) |
| = | 6 | x | x | ( | 9 | x | + | 1 | ) | − | 42 | x | ( | 9 | x | + | 1 | ) | − | 7 | ( | x | − | 7 | ) | ( | 9 | x | + | 1 | ) |
| = | 6 | x | x | × | 9 | x | + | 6 | x | x | × | 1 | − | 42 | x | ( | 9 | x | + | 1 | ) |
| = | 54 | x | x | x | + | 6 | x | x | − | 42 | x | ( | 9 | x | + | 1 | ) | − | 7 | ( | x | − | 7 | ) |
| = | 54 | x | x | x | + | 6 | x | x | − | 42 | x | × | 9 | x | − | 42 |
| = | 54 | x | x | x | + | 6 | x | x | − | 378 | x | x | − | 42 | x |
| = | 54 | x | x | x | + | 6 | x | x | − | 378 | x | x | − | 42 | x |
| = | 54 | x | x | x | + | 6 | x | x | − | 378 | x | x | − | 42 | x |
| = | 54 | x | x | x | + | 6 | x | x | − | 378 | x | x | − | 42 | x |
| = | 54 | x | x | x | + | 6 | x | x | − | 378 | x | x | − | 42 | x |
| = | 54 | x | x | x | + | 6 | x | x | − | 378 | x | x | − | 49 | x |
| = | 54 | x | x | x | + | 6 | x | x | − | 378 | x | x | − | 49 | x |
| = | 54 | x | x | x | + | 6 | x | x | − | 378 | x | x | − | 49 | x |
| = | 54 | x | x | x | + | 6 | x | x | − | 378 | x | x | + | 392 | x |
| 54 | x | x | x | + | 6 | x | x | − | 378 | x | x | + | 392 | x | = | 0 |
| x1= | - | 1 9 |
| x2= | 7 6 |
| x3=7 |