bonsoir
a) MD = 6-x
NB = 6-x
DC = BC = 6
Aire MDC = MD * DC/2 (* signifie multiplié par)
Aire MDC = (6-x)*6/2 = (6-x)*3 = 18-3x
Aire NBC = NB * BC/2 or NB=Md et BC=DC donc
Aire NBC = Aire MDC = 18-3x
b) Aire AMCN = Aire ABCD - Aire MDC - Aire NBC
Aire AMCN = Aire ABCD - 2*Aire MDC
Aire AMCN = 6*6 - 2(18-3x)
Aire AMCN = 36 - 36 + 6x
Aire AMCN = 6x
c) x = 2
Aire MDC = Aire NBc = 18 - 3*2 = 18-6 = 12 Cm²
Aire AMCN = 6*2 = 12 cm²
