It looks like you've uploaded an image containing a set of geometry problems written in Vietnamese. Let me help you analyze and solve the problems.

I'll summarize the content for you:

• Bài 1 (B1) involves a triangle $\Delta ABC$ with $AB = AC$, and points $M$ on segment $AC$ and $N$ on segment $AB$, with the given condition $AM = AN$.
• Bài 2 (B2) involves another geometric scenario where points $C$ and $D$ lie on the $Oxy$ plane, with conditions on the lengths $OA = OC$ and $AB = CD$.

The problems require proving certain geometric properties and relationships like congruence, parallelism, and perpendicularity.

Would you like a step-by-step solution for any of these problems? Feel free to specify which part you'd like to dive into!