\(M_{H_2}=1.2=2g/mol\\ M_{O_2}=16.2=32g/mol\\ M_{CO_2}=12+16.2=44g/mol\\ M_{Al_2O_3}=27.2+16.3=102g/mol\\ M_{Fe}=56g/mol\\ M_{Mg}=24g/mol\)

a) PTHH \(S+O_2\underrightarrow{t^o}SO_2\)

b) Khí SO₂ chính là chất làm cho chuột chết. Hợp chất này tên là lưu huỳnh đi-ô-xít (tên Tiếng Anh là sulfur dioxide). Đây là một oxit axit. 

As a responsible member of my family, I always strive to contribute and assist in various ways. I take on household chores such as cleaning, organizing, and tidying up the living spaces. Additionally, I help with grocery shopping and meal preparation, ensuring that everyone's dietary needs are met. I also assist my siblings with their homework and offer guidance whenever they need it. Furthermore, I actively participate in family discussions and decision-making processes, providing my input and suggestions. By actively engaging in these activities, I aim to alleviate the workload of my family members and create a harmonious and supportive environment for everyone.

I always try to be a helpful member of my family by doing various tasks around the house. I assist with household chores such as cleaning, laundry, and cooking. Additionally, I help my younger siblings with their homework and school projects. I am mindful of our family's budget by conserving energy and reducing waste. I also help with grocery shopping and finding the best deals. Being a responsible and helpful member of my family is important to me, and I will continue to do my part to make our home run smoothly.

a, (a² + b²).(c² + d²)

=   a².c² + a².d² + b².c² + b².d² (1)

(ac + bd)² + (ad - bc)²

= a².c² + 2abcd + b².d² + a².d² - 2abcd + b².c²

= a².c² + b².d² + a².d² + b².c²  (2)

Kết hợp (1) và (2) ta có:

(a²+b²).(c²+d²) = (ac + bd)² + (ad - bc)² (đpcm)

Bài 4 ý 2,

           (a + b + c)³

= (a+b)³ + 3(a+b)².c + 3.(a+b).c² + c³

= a³ + 3a²b+3ab² + b³ + 3.(a+b).[ (a + b).c + c²] + c³

= a³ + 3a²b + 3ab² + b³   +   3(a+b)[ac + bc + c²] + c³

= a³+b³+ c³ + 3ab.(a + b) + 3.(a + b)[ac + bc + c²] 

= a³ + b³ + c³ + 3.(a + b).(ab + ac + bc + c²]

= a³ + b³ + c³ + 3.(a + b).[(ab + bc) + (ac + c²)]

= a³ + b³ + c³ + 3.(a + b).[b.(a + c) + c.(a + c)]

= a³ + b³ + c³ + 3.(a + b).(a+c).(b+c) (đpcm)

A B C M N

Ta có

\(BC=4CM\Rightarrow\dfrac{CM}{BC}=\dfrac{1}{4}\Rightarrow\dfrac{CM}{BM}=\dfrac{1}{3}=\dfrac{CN}{AN}\)

=> MN//AB (Talet đảo trong tam giác)