bonjour
81² = (80+1)² = 80²+2*80*1 + 1² = 6400+160+1 = 6561
puisque (a+b)² = a² + 2ab + b²
48² = (50-2)² = 50²-2*50*2 + 2² = 2500-200+4 = 2304
puisque (a-b) = a² - 2ab + b²
63²-61² = (63-61) (63+61) = 2x124 = 248
et 49 x 51 = (50-1)² x (50+1)² = 50² - 1² = 2499
puisque a²-b² = (a+b) (a-b)
