( | 20 | − | x | ) | ( | 200 | − | 4 | x | ) | = | 4800 |
Left side of the equation = | 20 | ( | 200 | − | 4 | x | ) | − | x | ( | 200 | − | 4 | x | ) |
= | 20 | × | 200 | − | 20 | × | 4 | x | − | x | ( | 200 | − | 4 | x | ) |
= | 4000 | − | 80 | x | − | x | ( | 200 | − | 4 | x | ) |
= | 4000 | − | 80 | x | − | x | × | 200 | + | x | × | 4 | x |
= | 4000 | − | 280 | x | + | x | × | 4 | x |
4000 | − | 280 | x | + | x | × | 4 | x | = | 4800 |