а) 69 × 71 = (70 - 1) × (70 + 1) = 70^2 - 1^2 = 4900 - 1 = 4899
б) 58 × 62 = (60 - 2) × (60 + 2) = 60^2 - 2^2 = 3600 - 4 = 3596
а) 69 × 71 = (70 - 1) × (70 + 1) = 70^2 - 1^2 = 4900 - 1 = 4899
б) 58 × 62 = (60 - 2) × (60 + 2) = 60^2 - 2^2 = 3600 - 4 = 3596