6.
Daca P=24cm, l= 24/4, deci l= 6cm.
Ap= l/2, deci Ap=6/2=3 cm
8.Fie Δ ABC
D∈(AB), E∈(AC) si DE║BC.
AD=4cm; DB=6cm; AC=15 cm si BC=18 cm.
DE= ?
AD/AB=AE/AC=DE/BC
DECI:
BC=18
AD=4
DB=6, deci Ab= 4+6=10
AD/AB=4/10
AD/AB=DE/BC
4/10=DE/18
10 DE= 4*18
DE= 4*18:10=7.2 cm
