( | 200 | − | 160 | − | x | ) | ( | 20 | + | 2 | x | ) | = | 0 |
方程左边 = | 200 | ( | 20 | + | 2 | x | ) | − | 160 | ( | 20 | + | 2 | x | ) | − | x | ( | 20 | + | 2 | x | ) |
= | 200 | × | 20 | + | 200 | × | 2 | x | − | 160 | ( | 20 | + | 2 | x | ) | − | x | ( | 20 | + | 2 | x | ) |
= | 4000 | + | 400 | x | − | 160 | ( | 20 | + | 2 | x | ) | − | x | ( | 20 | + | 2 | x | ) |
= | 4000 | + | 400 | x | − | 160 | × | 20 | − | 160 | × | 2 | x | − | x | ( | 20 | + | 2 | x | ) |
= | 4000 | + | 400 | x | − | 3200 | − | 320 | x | − | x | ( | 20 | + | 2 | x | ) |
= | 800 | + | 80 | x | − | x | ( | 20 | + | 2 | x | ) |
= | 800 | + | 80 | x | − | x | × | 20 | − | x | × | 2 | x |
= | 800 | + | 60 | x | − | x | × | 2 | x |
800 | + | 60 | x | − | x | × | 2 | x | = | 0 |