Réponse :
ex3 factoriser pour calculer mentalement
A = 13 x 99 + 13 x 1 = 13(99 + 1) = 13 x 100 = 1300
B = 33 x 21 - 33 x 1 = 33(21 - 1) = 33 x 20 = 660
C = 70 x 1 + 70 x 49 = 70(1 + 49) = 70 x 50 = 35 00
D = 42 x 1007 - 42 x 7 = 42(1007 - 7) = 42 x 1000 = 42 000
E = 18 x 0.2 + 18 x 9.8 = 18(0.2 + 9.8) = 18 x 10 = 180
F = 51 x 7.8 - 5.8 x 51 = 51(7.8 - 5.8) = 51 x 2 = 102
Explications étape par étape
