The image you've uploaded seems to be a geometry problem in Vietnamese. Here's a summary of the problem and questions:

Problem 1:

Given a right triangle $\triangle ABC$ with $A$ as the right angle, and $H$ as the foot of the perpendicular from $A$ to $BC$, we are asked to prove:

a) $\triangle HBA = \triangle HBD$
b) $\triangle ABC = \triangle DBC$
c) $OB \perp DC$

Problem 2:

Given a triangle $\triangle ABC$ where $AB = AC$, and $H$ is the foot of the perpendicular from $A$ to $BC$, we need to prove:

a) $\triangle AHB = \triangle AHC$
b) $AH$ is the perpendicular bisector of $BC$, and $H$ is the midpoint of $BC$
c) $HM \perp AB$ at $M$, and $HN \perp AC$ at $N$, proving $\triangle AHM = \triangle AHN$
d) $AH \perp MN$, and $MN \parallel BC$

These are geometric proofs involving congruency and perpendicularity in right triangles and isosceles triangles.

Would you like to proceed with detailed solutions for these questions?