a)
BC=20
DC=9BD
BC=BD+9BD=10BD=20
BD=20:10=2 cm
DC=18 cm
AD=√2*18=√36=6 cm
b)BC=26
DB/DC=4/9
DC=9DB/4
BC=BD+9BD/4=13BD/4=26
BD=26*4/13=8 cm
DC=26-8=18 cm
AD=√8*18=√144=12 cm
c) Bd, CD si AD daca BC= 34 cm si DB reprezinta 70% din DC
BC=34
DB=70%DC=7DC/10
DC=10DB/7
BC=BD+10BD/7=17BD/7=34
BD=34*7/17=14 cm
DC=34-14=20 cm
AD=√14*20=√280=2√70 cm