Question

Answer 1

áp dụng định lý talet ta có:

\(\dfrac{AB}{AC}=\dfrac{AD}{AE}\)

\(\Leftrightarrow\dfrac{5}{6}=\dfrac{7,5}{AE}\Leftrightarrow5AE=6.7,5\)

\(\Leftrightarrow AE=9\)

Answer 2

Xét ΔACE có BD//CE

nên AB/AC=AD/AE

=>\(\dfrac{7.5}{AE}=\dfrac{5}{6}\)

hay AE=9(cm)

=>DE=9-7,5=1,5(cm)