Răspuns:
a) DE//BC=> triungh>ADE asemenea cu ABC
AD/AB =AE/AC =DE=BC
4/14 =8/BC
BC=14*8/4 =28 cm
DE/BC=AE/AC
8/28=10/AE
AE=28*10/8 =35 cm
Pabc =AB+BC+AC =14+28+35 =77 cm
Explicație pas cu pas:
b) DE//BC
=>AD/AB=DE/BC=AE/AC
6/AB =10/15
AB=6*15/10 =9 cm
DE/BC=AE/AC
10/15=8/AC
AC =15*8/10 =12cm
Pabc =AB+BC+AC =9+15+12 =36 cm