A=AB*AD
72=(x+7)(x+1)
72=x^2+7x+x+7
x^2+8x-65=0
Delta=64+260=324⇒√delta=18
x1,2=-8+-18/2
x1=10/2=5 apartine lui N
x2=-26/2=-13 nu apartine lui N
AB=7+5=12cm
AD=5+1=6cm
a)EB=AB/2 deci EB=6 cm
Abec=6*6/2=18 cm^2
Aabc=12*6/2=36cm^2
Aaec=Aabc-Abec
Aaec=36-18=18cm^2
b)AC^2=AB^2+BC^2
AC^2=144+36
AC^2=180 rezulta AC=6√5 cm
AE||DC⇒AEF~CDF⇒AE/CD=AF/FC( adunam numaratorul la numitor)⇒
⇒6/18=AF/6√5⇒AF=6*6√5/18=2√5 cm
