The image contains three mathematical questions about functions (hàm ánh) and their properties.

Question 1: "g có phải đơn ánh không?"

This question asks whether the function $g$ is injective (one-to-one).

The function $g$ is defined from the set $\{1, 2, 3, 4\}$ to the set $\{a, b, c, d\}$, with the following mappings: $g(1) = 2, \quad g(b) = 1, \quad g(c) = 3, \quad g(d) = 2$

Since $g(d) = g(1) = 2$, the function is not injective because two different inputs (1 and $d$) map to the same output (2). So, the answer is Sai (False).

Question 2: "Hàm f là hàm gì?"

This question asks for the type of function $f$. The function $f$ maps $\{1, 2, 3, 4\}$ to $\{a, b, c, d\}$ as follows: $f(1) = d, \quad f(2) = c, \quad f(3) = a, \quad f(4) = b$

Since every element in the domain $\{1, 2, 3, 4\}$ is mapped to a unique element in the codomain $\{a, b, c, d\}$, the function is bijective (toàn ánh).

So, the correct answer is toàn ánh.

Question 3: "Một công ty có 10 bộ phận..."

This question is about a function mapping employees to departments, where every employee is assigned to one department, and each department has at least one employee. This describes a surjective (onto) function because every department is filled (no department is left empty).

So, the correct answer is toàn ánh.

Would you like a more detailed explanation of any part of this? Here are some related questions:

1. What is the difference between injective, surjective, and bijective functions?
2. How can you check if a function is injective?
3. What real-life examples correspond to injective and surjective functions?
4. What happens if a function is neither injective nor surjective?
5. Can a function be injective but not surjective?

Tip: When analyzing functions, carefully check how inputs map to outputs, especially to verify if the mapping is unique or covers the entire range.