Question

abc un triunghi oarecare, E apartine (ab),F apartine (ac) aratati ca EFparalelBC daca
a.AE=4; AB=16; AC=20;    FC=15
b. AB=28; EB=21; AF=6; FC=18
VA ROGGG !!!! URGENTTT!!!

Answer 1

a.AE=4 cm
AB=16 cm
AC=20 cm
FC=15 cm
AF=AC-FC
AF=20-15=5 cm
$\frac{AE}{AB} = \frac{AF}{AC}$  ⇒ $\frac{4}{16} = \frac{5}{20}$  ⇒ $\frac{1}{4} = \frac{1}{4}$   *simplificam la prima cu 4,iar la a doua cu 5* 
⇒*teorema reciproca a lui Thales* EF II BC

b.AB=28 cm
EB=21 cm
AF=6 cm
FC=18 cm
AE=AB-EB
AE=28-21=7 cm
$\frac{AE}{EB} = \frac{AF}{FC}$ ⇒ $\frac{7}{21} = \frac{6}{18}$ ⇒  $\frac{1}{3} = \frac{1}{3}$ *simplificam la prima cu 7 ,iar la a doua cu 6* ⇒*teorema reciproca a lui Thales* EF II BC