| 40 | ( | x | + | 1 | ) | ( | x | + | 1 | ) | = | 242 5 |
| Left side of the equation = | 40 | x | ( | x | + | 1 | ) | + | 40 | × | 1 | ( | x | + | 1 | ) |
| = | 40 | x | ( | x | + | 1 | ) | + | 40 | ( | x | + | 1 | ) |
| = | 40 | x | x | + | 40 | x | × | 1 | + | 40 | ( | x | + | 1 | ) |
| = | 40 | x | x | + | 40 | x | + | 40 | ( | x | + | 1 | ) |
| = | 40 | x | x | + | 40 | x | + | 40 | x | + | 40 | × | 1 |
| = | 40 | x | x | + | 40 | x | + | 40 | x | + | 40 |
| = | 40 | x | x | + | 80 | x | + | 40 |
| 40 | x | x | + | 80 | x | + | 40 | = | 242 5 |
| x1= | - | 21 10 |
| x2= | 1 10 |