The image you uploaded contains two geometry problems written in Vietnamese. Here's a brief translation of the tasks:

B1: For triangle $\Delta ABC$, where $AB = AC$:

• Let $M$ be on segment $AC$ and $N$ on segment $AB$, with the conditions $AM = AN$.
• Prove the following:
  • (a) $\triangle ABM = \triangle ACN$
  • (b) Point $I$ is where the perpendiculars from $BM$ and $CN$ meet.
  • (c) $\triangle INB = \triangle INC$
  • (d) Prove that line $MN \parallel BC$.

B2: For the circle $xOy$, with points $C$, $D \in xOy$, such that $OA = OC$ and $AB = CD$:

• Prove the following:
  • (a) $\triangle OAD = \triangle OBC$
  • (b) Let $M$ be the intersection of $BC$ and $AD$, proving $\triangle AMB = \triangle MDC$
  • (c) Prove that $OM$ is perpendicular to line $x$.
  • (d) Prove that $OM$ is perpendicular to $AC$.
  • (e) Prove that $AC \parallel BD$.

If you need help with solving any part of these problems, let me know which one you'd like to work on first!