| ( | 1 | + | 2 | y | ) | ( | 1 | − | 2 | y | ) | = | 0 |
| Left side of the equation = | 1 | ( | 1 | − | 2 | y | ) | + | 2 | y | ( | 1 | − | 2 | y | ) |
| = | 1 | × | 1 | − | 1 | × | 2 | y | + | 2 | y | ( | 1 | − | 2 | y | ) |
| = | 1 | − | 2 | y | + | 2 | y | ( | 1 | − | 2 | y | ) |
| = | 1 | − | 2 | y | + | 2 | y | × | 1 | − | 2 | y | × | 2 | y |
| = | 1 | − | 2 | y | + | 2 | y | − | 4 | y | y |
| = | 1 | − | 0 | y | − | 4 | y | y |
| 1 | − | 0 | y | − | 4 | y | y | = | 0 |
| y1= | - | 1 2 |
| y2= | 1 2 |