( | 120 | − | 75 | − | x | ) | ( | 400 | + | 3 | x | ) | = | 13350 |
方程左边 = | 120 | ( | 400 | + | 3 | x | ) | − | 75 | ( | 400 | + | 3 | x | ) | − | x | ( | 400 | + | 3 | x | ) |
= | 120 | × | 400 | + | 120 | × | 3 | x | − | 75 | ( | 400 | + | 3 | x | ) | − | x | ( | 400 | + | 3 | x | ) |
= | 48000 | + | 360 | x | − | 75 | ( | 400 | + | 3 | x | ) | − | x | ( | 400 | + | 3 | x | ) |
= | 48000 | + | 360 | x | − | 75 | × | 400 | − | 75 | × | 3 | x | − | x | ( | 400 | + | 3 | x | ) |
= | 48000 | + | 360 | x | − | 30000 | − | 225 | x | − | x | ( | 400 | + | 3 | x | ) |
= | 18000 | + | 135 | x | − | x | ( | 400 | + | 3 | x | ) |
= | 18000 | + | 135 | x | − | x | × | 400 | − | x | × | 3 | x |
= | 18000 | − | 265 | x | − | x | × | 3 | x |
18000 | − | 265 | x | − | x | × | 3 | x | = | 13350 |
x1= | - | 310 3 |
x2=15 |