( | 300 | − | 10 | x | ) | ( | x | − | 10 | ) | = | 0 |
方程左边 = | 300 | ( | x | − | 10 | ) | − | 10 | x | ( | x | − | 10 | ) |
= | 300 | x | − | 300 | × | 10 | − | 10 | x | ( | x | − | 10 | ) |
= | 300 | x | − | 3000 | − | 10 | x | ( | x | − | 10 | ) |
= | 300 | x | − | 3000 | − | 10 | x | x | + | 10 | x | × | 10 |
= | 300 | x | − | 3000 | − | 10 | x | x | + | 100 | x |
= | 400 | x | − | 3000 | − | 10 | x | x |
400 | x | − | 3000 | − | 10 | x | x | = | 0 |