( | 20 | − | x | ) | ( | 300 | + | 20 | x | ) | = | 3000 |
Left side of the equation = | 20 | ( | 300 | + | 20 | x | ) | − | x | ( | 300 | + | 20 | x | ) |
= | 20 | × | 300 | + | 20 | × | 20 | x | − | x | ( | 300 | + | 20 | x | ) |
= | 6000 | + | 400 | x | − | x | ( | 300 | + | 20 | x | ) |
= | 6000 | + | 400 | x | − | x | × | 300 | − | x | × | 20 | x |
= | 6000 | + | 100 | x | − | x | × | 20 | x |
6000 | + | 100 | x | − | x | × | 20 | x | = | 3000 |