Question

Answer 1

Hình 1: 

Xét ΔBAC có MN//AC

nên \(\dfrac{NM}{AC}=\dfrac{BM}{BC}=\dfrac{BN}{BA}\)

=>4/y=x/(x+4,5)=2/5

=>y=10(cm); 5x=2x+9

=>y=10; x=3

Answer 2

a, Theo định lí Ta lét 

\(\dfrac{BN}{NA}=\dfrac{BM}{MC}\Rightarrow BM=\dfrac{BN.MC}{NA}=3\)

Theo hệ quả Ta lét 

\(\dfrac{BN}{AB}=\dfrac{MN}{AC}\Rightarrow\dfrac{2}{5}=\dfrac{4}{AC}\Leftrightarrow AC=10\)

b, Vì EH là pg tam giác FED nên 

\(\dfrac{FE}{ED}=\dfrac{FH}{HD}\Leftrightarrow\dfrac{6}{5}=\dfrac{8-HD}{HD}\Leftrightarrow6HD=40-5HD\Leftrightarrow HD=\dfrac{40}{11}\)