| ( | 1 | + | 10 | x | ) | ( | 1 | + | 2 | x | ) | ( | 1 | + | 1 5 | x | ) | + | 20 | = | 0 |
| Left side of the equation = | 1 | ( | 1 | + | 2 | x | ) | ( | 1 | + | 1 5 | x | ) | + | 10 | x | ( | 1 | + | 2 | x | ) | ( | 1 | + | 1 5 | x | ) | + | 20 |
| = | 1 | × | 1 | ( | 1 | + | 1 5 | x | ) | + | 1 | × | 2 | x | ( | 1 | + | 1 5 | x | ) | + | 10 | x | ( | 1 | + | 2 | x | ) | ( | 1 | + | 1 5 | x | ) | + | 20 |
| = | 1 | ( | 1 | + | 1 5 | x | ) | + | 2 | x | ( | 1 | + | 1 5 | x | ) | + | 10 | x | ( | 1 | + | 2 | x | ) | ( | 1 | + | 1 5 | x | ) | + | 20 |
| = | 1 | × | 1 | + | 1 | × | 1 5 | x | + | 2 | x | ( | 1 | + | 1 5 | x | ) | + | 10 | x | ( | 1 | + | 2 | x | ) | ( | 1 | + | 1 5 | x | ) |
| = | 1 | + | 1 5 | x | + | 2 | x | ( | 1 | + | 1 5 | x | ) | + | 10 | x | ( | 1 | + | 2 | x | ) | ( | 1 | + | 1 5 | x | ) | + | 20 |
| = | 21 | + | 1 5 | x | + | 2 | x | ( | 1 | + | 1 5 | x | ) | + | 10 | x | ( | 1 | + | 2 | x | ) | ( | 1 | + | 1 5 | x | ) |
| = | 21 | + | 1 5 | x | + | 2 | x | × | 1 | + | 2 | x | × | 1 5 | x | + | 10 | x |
| = | 21 | + | 1 5 | x | + | 2 | x | + | 2 5 | x | x | + | 10 | x | ( | 1 | + | 2 | x | ) | ( | 1 | + | 1 5 | x | ) |
| = | 21 | + | 11 5 | x | + | 2 5 | x | x | + | 10 | x | ( | 1 | + | 2 | x | ) | ( | 1 | + | 1 5 | x | ) |
| = | 21 | + | 11 5 | x | + | 2 5 | x | x | + | 10 | x | × | 1 | ( | 1 | + | 1 5 | x | ) | + | 10 | x |
| = | 21 | + | 11 5 | x | + | 2 5 | x | x | + | 10 | x | ( | 1 | + | 1 5 | x | ) | + | 20 | x | x |
| = | 21 | + | 11 5 | x | + | 2 5 | x | x | + | 10 | x | × | 1 | + | 10 | x | × | 1 5 |
| = | 21 | + | 11 5 | x | + | 2 5 | x | x | + | 10 | x | + | 2 | x | x | + | 20 |
| = | 21 | + | 61 5 | x | + | 2 5 | x | x | + | 2 | x | x | + | 20 | x | x |
| = | 21 | + | 61 5 | x | + | 2 5 | x | x | + | 2 | x | x | + | 20 | x | x |
| = | 21 | + | 61 5 | x | + | 2 5 | x | x | + | 2 | x | x | + | 20 | x | x |
| 21 | + | 61 5 | x | + | 2 5 | x | x | + | 2 | x | x | + | 20 | x | x | = | 0 |