( | 36 | − | 2 | x | ) | ( | 20 | − | x | ) | = | 576 |
Left side of the equation = | 36 | ( | 20 | − | x | ) | − | 2 | x | ( | 20 | − | x | ) |
= | 36 | × | 20 | − | 36 | x | − | 2 | x | ( | 20 | − | x | ) |
= | 720 | − | 36 | x | − | 2 | x | ( | 20 | − | x | ) |
= | 720 | − | 36 | x | − | 2 | x | × | 20 | + | 2 | x | x |
= | 720 | − | 36 | x | − | 40 | x | + | 2 | x | x |
= | 720 | − | 76 | x | + | 2 | x | x |
720 | − | 76 | x | + | 2 | x | x | = | 576 |