1) Ta có:
3452 = 345 × 345 = (342 + 3) × 345 = 342 × 345 + 3 × 345
342 × 348 = 342 × (345 + 3) = 342 × 345 + 342 × 3
Vì 3 x 345 > 342 × 3
=> 3452 > 342 × 348
2) Ta có:
8742 = 874 × 874 = (870 + 4) × 874 = 870 × 874 + 4 × 874
870 × 878 = 870 × (874 + 4) = 870 × 874 + 870 × 4
Vì 4 × 874 > 870 × 4
=> 8742 > 870 × 878