1) 2.1² - 0.9² = 4.41 + 0.81 = 5.22
2) (2.1 - 0.9)²= 1.2² = 1.44
3) ( 2.1 - 0.9) × (2.1 + 0.9) = 1.2 × 3 = 3.6
1) 2.1² - 0.9² = 4.41 + 0.81 = 5.22
2) (2.1 - 0.9)²= 1.2² = 1.44
3) ( 2.1 - 0.9) × (2.1 + 0.9) = 1.2 × 3 = 3.6