Question

Answer 1

Áp dụng định lí Ta-let ta có: \(\dfrac{PD}{PE}=\dfrac{DQ}{QF}\Leftrightarrow\dfrac{x}{5}=\dfrac{4}{12-4}\Rightarrow x=2,5\)

Answer 2

có PQ//EF (GT)

⇒\(\dfrac{DP}{PE}\)=\(\dfrac{DQ}{QF}\) (Định lý Ta-lét)

⇒\(\dfrac{x}{5}\)=\(\dfrac{4}{12-4}\)

⇒x=\(\dfrac{5\cdot4}{8}\)

⇒x=2,5

vậy x=2,5