Răspuns:
Explicație pas cu pas:
DE║BC Teorema Thales
AD/DB=1/4 AD/(AD+DB)=1/(1+4)1/5=AD/AB
AE/EC=AD/DB=1/4
AE/AC=AD/AB=1/5
AE/AC=1/5=AC/(AC-AE)=AC/EC=5/(5-1)=5/4