Question

giúp mình

Answer 1

\(\text{a)Xét }\Delta ABC\text{ có:}\)

\(MN//EF\left(gt\right)\)

\(\Rightarrow\dfrac{AM}{MC}=\dfrac{AN}{NC}\left(\text{định lí Ta-lét}\right)\)

\(\Rightarrow\dfrac{12}{6}=\dfrac{x}{8}\Rightarrow x=\dfrac{12.8}{6}=16\left(cm\right)\)

\(\text{b)DE=DM+ME=9,5+28=37,5(cm)}\)

\(\text{Xét }\Delta DMN\text{ và }\Delta DEF\text{ có:}\)

\(MN//EF\left(gt\right)\)

\(\Rightarrow\dfrac{DM}{DE}=\dfrac{MN}{EF}\left(\text{hệ quả Ta-lét}\right)\)

\(\Rightarrow\dfrac{9,5}{37,5}=\dfrac{8}{x}\Rightarrow x=\dfrac{37,5.8}{9,5}\approx31,58\left(cm\right)\)