Bonsoir,
25×19 = 25 ×(20-1) = 25×20 - 25×1 = 500 - 25 = 475
102×37 = 100 × 37 + 2×37 = 3700 + 74 = 3774
998 × 45 = 1000 × 45 - 2 × 45 = 45 000 - 90 = 44 910
54 × 11 = 54 × 10 + 54 × 1 = 540 + 54 = 594
65 × 247 = 65 × 200 + 65 × 50 - 65 × 3 = 13 000 + 3 250 - 195
= 16 250 - 195 = 16 055
101 × 247 = 100 × 247 + 1 × 247 = 24 700 + 247 = 24 947
Démonstration
3(2x - 6) + 18 = 6x ;
6x - 18 + 18 = 6x ;
6x = 6x
