Bonsoir,
n et m : 2 nombres
n + m = 300
a) conjecturer :
n = 100
m = 200
nm = 100 x 200 = 20000
(n + 7)(m + 7) = nm + 7n + 7m + 49
(n + 7)(m + 7) = 20000 + 700 + 1400 + 49
(n + 7)(m + 7) = 22149
22149 - 20000 = 2149
b) démarche :
= nm + 7n + 7m + 49
= nm + 7(n + m + 7)
= nm + 7(300 + 7)
= nm + 7 x 307
= nm + 2149
