( | 18 | − | 2 | x | − | 15 | ) | ( | 54 | − | 4 | x | ) | = | 400 |
方程左边 = | 18 | ( | 54 | − | 4 | x | ) | − | 2 | x | ( | 54 | − | 4 | x | ) | − | 15 | ( | 54 | − | 4 | x | ) |
= | 18 | × | 54 | − | 18 | × | 4 | x | − | 2 | x | ( | 54 | − | 4 | x | ) | − | 15 | ( | 54 | − | 4 | x | ) |
= | 972 | − | 72 | x | − | 2 | x | ( | 54 | − | 4 | x | ) | − | 15 | ( | 54 | − | 4 | x | ) |
= | 972 | − | 72 | x | − | 2 | x | × | 54 | + | 2 | x | × | 4 | x | − | 15 | ( | 54 | − | 4 | x | ) |
= | 972 | − | 72 | x | − | 108 | x | + | 8 | x | x | − | 15 | ( | 54 | − | 4 | x | ) |
= | 972 | − | 180 | x | + | 8 | x | x | − | 15 | ( | 54 | − | 4 | x | ) |
= | 972 | − | 180 | x | + | 8 | x | x | − | 15 | × | 54 | + | 15 | × | 4 | x |
= | 972 | − | 180 | x | + | 8 | x | x | − | 810 | + | 60 | x |
= | 162 | − | 120 | x | + | 8 | x | x |
162 | − | 120 | x | + | 8 | x | x | = | 400 |