Cho hình vẽ sau. Chọn khẳng định sai?
\(\dfrac{AD}{AB}=\dfrac{AE}{AC}\) \(\Rightarrow\) \(DE\)//\(BC\).\(\dfrac{AD}{BD}=\dfrac{AE}{CE}\) \(\Rightarrow\) \(DE\)//\(BC\).\(\dfrac{AD}{BD}=\dfrac{AC}{EC}\) \(\Rightarrow\) \(DE\)//\(BC\).\(\dfrac{AD}{DE}=\dfrac{AE}{ED}\) \(\Rightarrow\) \(DE\)//\(BC\).