( | 20 | − | 2 | x | ) | ( | 10 | − | 2 | x | ) | = | 128 |
Left side of the equation = | 20 | ( | 10 | − | 2 | x | ) | − | 2 | x | ( | 10 | − | 2 | x | ) |
= | 20 | × | 10 | − | 20 | × | 2 | x | − | 2 | x | ( | 10 | − | 2 | x | ) |
= | 200 | − | 40 | x | − | 2 | x | ( | 10 | − | 2 | x | ) |
= | 200 | − | 40 | x | − | 2 | x | × | 10 | + | 2 | x | × | 2 | x |
= | 200 | − | 40 | x | − | 20 | x | + | 4 | x | x |
= | 200 | − | 60 | x | + | 4 | x | x |
200 | − | 60 | x | + | 4 | x | x | = | 128 |