( | 10 | + | x | ) | ( | 280 | − | 10 | x | ) | = | 3120 |
Left side of the equation = | 10 | ( | 280 | − | 10 | x | ) | + | x | ( | 280 | − | 10 | x | ) |
= | 10 | × | 280 | − | 10 | × | 10 | x | + | x | ( | 280 | − | 10 | x | ) |
= | 2800 | − | 100 | x | + | x | ( | 280 | − | 10 | x | ) |
= | 2800 | − | 100 | x | + | x | × | 280 | − | x | × | 10 | x |
= | 2800 | + | 180 | x | − | x | × | 10 | x |
2800 | + | 180 | x | − | x | × | 10 | x | = | 3120 |