| 140 | ÷ | ( | x | − | 10 | ) | − | 140 | ÷ | ( | x | + | 10 | ) | = | 15 |
| Multiply both sides of the equation by: | ( | x | − | 10 | ) |
| 140 | − | 140 | ÷ | ( | x | + | 10 | ) | × | ( | x | − | 10 | ) | = | 15 | ( | x | − | 10 | ) |
| 140 | − | 140 | ÷ | ( | x | + | 10 | ) | × | x | + | 140 | ÷ | ( | x | + | 10 | ) | × | 10 | = | 15 | ( | x | − | 10 | ) |
| 140 | − | 140 | ÷ | ( | x | + | 10 | ) | × | x | + | 140 | ÷ | ( | x | + | 10 | ) | × | 10 | = | 15 | x | − | 15 | × | 10 |
| 140 | − | 140 | ÷ | ( | x | + | 10 | ) | × | x | + | 1400 | ÷ | ( | x | + | 10 | ) | = | 15 | x | − | 150 |
| Multiply both sides of the equation by: | ( | x | + | 10 | ) |
| 140 | ( | x | + | 10 | ) | − | 140 | x | + | 1400 | = | 15 | x | ( | x | + | 10 | ) | − | 150 | ( | x | + | 10 | ) |
| 140 | x | + | 140 | × | 10 | − | 140 | x | + | 1400 | = | 15 | x | ( | x | + | 10 | ) | − | 150 | ( | x | + | 10 | ) |
| 140 | x | + | 140 | × | 10 | − | 140 | x | + | 1400 | = | 15 | x | x | + | 15 | x | × | 10 | − | 150 | ( | x | + | 10 | ) |
| 140 | x | + | 1400 | − | 140 | x | + | 1400 | = | 15 | x | x | + | 150 | x | − | 150 | ( | x | + | 10 | ) |
| 0 | x | + | 2800 | = | 15 | x | x | + | 150 | x | − | 150 | ( | x | + | 10 | ) |
| 2800 | = | 15 | x | x | + | 150 | x | − | 150 | x | − | 150 | × | 10 |
| 2800 | = | 15 | x | x | + | 150 | x | − | 150 | x | − | 1500 |
| 2800 | = | 15 | x | x | + | 0 | x | − | 1500 |
| x1= | - | √860 √3 |
| x2= | √860 √3 |