Lời giải
a)
\(\Delta OMB\approx\Delta OND\Rightarrow\dfrac{OB}{OD}=\dfrac{OM}{ON}\)
\(\left\{{}\begin{matrix}OM+ON=5\\\dfrac{OM}{ON}=\dfrac{1,5}{4,5}=\dfrac{1}{3}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}OM+ON=5\\3OM-ON=0\end{matrix}\right.\)\(\Leftrightarrow\left\{{}\begin{matrix}OM=\dfrac{5}{4}\left(cm\right)\\ON=\dfrac{15}{4}\left(cm\right)\end{matrix}\right.\)
a) \(\dfrac{5}{4}=1,25\Rightarrow DA\left(A\right)\)
b) \(\dfrac{15}{4}=3+\dfrac{3}{4}=3,75\rightarrow PA\left(C\right)\)