Question

Answer 1

Bài 3:

ΔABC vuông tại A

=>\(AB^2+AC^2=BC^2\)

=>\(BC^2=3^2+4^2=25\)

=>BC=5(cm)

AM+MB=AB

=>MB+1=4

=>MB=3(cm)

Xét ΔABC có MN//AC

nên \(\dfrac{BM}{BA}=\dfrac{BN}{BC}\)

=>\(\dfrac{BN}{5}=\dfrac{3}{4}\)

=>BN=3,75(cm)

Bài 2:

AM+MB=AB

=>AB=4+6

=>AB=10(cm)

Xét ΔABC có MN//BC

nên \(\dfrac{AM}{AB}=\dfrac{AN}{AC}\)

=>\(\dfrac{AN}{20}=\dfrac{4}{10}=\dfrac{8}{20}\)

=>AN=8(cm)