Răspuns:
a. ΔABC, [DE] l.m => DE ║ BC, DE=BC/2 => BC=2*DE=2*6 cm=12 cm
in trapezul BCED, [MN] lm => MN=B+b/2= BC+DE/2
MN= 12+6/2=18/2=9 cm
T.f.a
b. DE║ BC ===> ΔADE ~ ΔABC
=> A ADE/ A ABC= k², unde k= rap. de asemanare= DE/BC= 6/12=1/2
=> A ADE/ A ABC= (1/2)²= 1/4
=> A ADE/ A ABC- A ADE= 1/4-1
<=> A/ ADE/ A BCED= 1/3
<=> 24/ A BCED= 1/3
=> A BCED= 3*24=72 cm²
