| ( | 17 20 | − | 3 400 | x | ) | ( | 13 10 | + | 3 200 | x | ) | = | 0 |
| 方程左边 = | 17 20 | ( | 13 10 | + | 3 200 | x | ) | − | 3 400 | x | ( | 13 10 | + | 3 200 | x | ) |
| = | 17 20 | × | 13 10 | + | 17 20 | × | 3 200 | x | − | 3 400 | x | ( | 13 10 | + | 3 200 | x | ) |
| = | 221 200 | + | 51 4000 | x | − | 3 400 | x | ( | 13 10 | + | 3 200 | x | ) |
| = | 221 200 | + | 51 4000 | x | − | 3 400 | x | × | 13 10 | − | 3 400 | x | × | 3 200 | x |
| = | 221 200 | + | 51 4000 | x | − | 39 4000 | x | − | 9 80000 | x | x |
| = | 221 200 | + | 3 1000 | x | − | 9 80000 | x | x |
221 200 | + | 3 1000 | x | − | 9 80000 | x | x | = | 0 |
| x1= | - | 260 3 |
| x2= | 340 3 |