AM=1/4 AB
DN=1/4DC=1/4 AB ( pt ca AB=DC in paralelogram)
DN≡AM
DN|| AM
2 laturi opuse paralele si congruente AMND poaralelofram, cerinta
MB=AB-AM= 4AM-AM=3AM
NC=DC-DN=4DN-DN=3DN=3AM (la pct am arata ca AM≡DN)
dar NC||MB
2 lauti opuse paralele si congruete, MBCN paralelogram, cerinta