Из условия \( \frac{AB}{BD} = \frac{1}{2} \) и \( AB = 3 \) следует:
\(\begin{align*}\) \(\frac{3}{BD}\) &= \(\frac{1}{2}\) \\ BD &= 3 \(\times\) 2 \\ BD &= 6 \(\end{align*}\)Из условия \( \frac{BD}{DC} = \frac{4}{1} \) и \( BD = 6 \) следует:
\(\begin{align*}\) \(\frac{6}{DC}\) &= \(\frac{4}{1}\) \\ 4 \(\cdot\) DC &= 6 \\ DC &= \(\frac{6}{4}\) \\ DC &= \(\frac{3}{2}\) \\ DC &= 1.5 \(\end{align*}\)Ответ: BD = 6, DC = 1.5.