bonjour,
B,C et D alignés
on appelle x la longueur BC
P ABC = 3x
CD = (11-x)
P CDEF = 4(11-x) = 44-4x
on résous :
3x = 44-4x
3x+4x = 44
7x = 44/7
si BC = 44/7(cm) P ABC = P ABCD
P ABC = 3*44/7 = 132/7
P CDEF = 4(11-4x) = 44-4x = 44-(4*44/7) = 44-176/7 =(308-176)/7 = 132/7