lạc lạc 

Huhu, bài này không khó đâu ạ. =((( 

UwU Câu a bị lỗi mất tiêu. 

Chọn mốc thời gian lúc xe bắt đầu xuất phát, chiều dương là chiều chuyển động của xe. 

a. Ta có \(s_1=v_ot+\dfrac{1}{2}at_1^2\) \(\Leftrightarrow50=0+\dfrac{1}{2}a.10^2\) \(\Leftrightarrow a=1\) (m/s^2) 

\(F=ma=5000.1=5000\left(N\right)\)

\(F_k=F+F_c=5000+1000=6000\left(N\right)\)

b. \(v_2=v_0+at_2\) \(\Leftrightarrow\) \(v_2=20\) (m/s) 

\(s_2=\dfrac{1}{2}at_2^2=\dfrac{1}{2}.1.20^2=200\left(m\right)\)

c.  \(v_3^2-v_0^2=2a_3s_3\) \(\Leftrightarrow10^2-0=2.10.a_3\) \(\Leftrightarrow a_3=5\) (m/s^2) 

\(F_3=ma_3=5000.5=25000\left(N\right)\)

\(F_{k3}=25000+1000=26000\left(N\right)\)

1- There is no water left in the nearby well. 
2- He is now studying in the USA as an exchange student.
3- He was a good collector of coins. 
4-Japan is said to be a mountainous country.
5- Finding the film is uninteresting we turned the TV off. 
6- The growth of trees occurs very slowly. 
7- Most students go picnic when they have one Saturday off. 
8- Some pack trips to Thailand are surprisingly cheap. 
9- We were surprised at what they are talking about.
10- Where’s Bermuda? Can you tell me its location? 
11- The show brought enjoyment to millions of viewers.

12- Most of the villagers have lived here all their lives.
13- She listens to music for relaxation.
14- I find this piece of music very restful
15- He made a collection of Roman coins and medals.
16- We had an exchange student from Spain staying with us last year.
17- We spent an enjoyable evening talking about old times.
18- To our amazing, he swallowed a sword.
19- I was amazed at the depth of her knowledge.
20- We stayed at a hotel with a restful atmosphere. 
21- They hurriedly gather their things and ran to the bus stop. 
22- Thousands are going hungry because of the failure of this year’s harvest. 
23- The poor children gazed hungrily at the display of food 
24- A growing number of people are returning to full-time education.

Gọi (d) y = ax + b là đường thẳng đi qua 2 điểm \(A\left(1\text{;}4\right)\) và \(B\left(-1\text{;}2\right)\) 

Khi đó \(\left\{{}\begin{matrix}4=a.1+b\\2=-1.a+b\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}a=1\\b=3\end{matrix}\right.\)

Vậy đường thẳng (d) có phương trình là \(y=x+3\)

Thế tọa độ \(C\left(-2\text{;}1\right)\) vào (d) ta thấy C thuộc (d) 

Vậy 3 điểm A, B, C thẳng hàng. 

\(y=mx^3+2mx^2+\left(1-m\right)x+3-2m\)

\(\Leftrightarrow\left(x^3+2x^2-x-2\right)m+\left(x-y+3\right)=0\)

Gọi \(\left(x_0\text{;}y_0\right)\) là điểm cố định mà đồ thị hàm số đi qua. 

\(\Leftrightarrow\left\{{}\begin{matrix}x_0^3+2x_0^2-x_0-2=0\left(a\right)\\x_0-y_0+3=0\end{matrix}\right.\)

PT (a) có 3 nghiệm phân biệt nên đồ thị hàm số luôn đi qua 3 điểm cố định. 

Giải pt ra 3 điểm đó là \(A\left(1\text{;}4\right),B\left(-1\text{;}2\right),C\left(-2\text{;}1\right)\)

\(\overrightarrow{AB}=\left(-2\text{;}-2\right)\)

\(\overrightarrow{AC}=\left(-3\text{;}-3\right)\)

\(\overrightarrow{AB}=\dfrac{2}{3}\overrightarrow{AC}\) => Vector AB và vector AC cùng hướng. 

Vậy 3 điểm A, B, C thẳng hàng. 

Đề thiếu m ở 3 hoặc -2 rồi ạ. 

Hợp chất của A với Oxi là \(AO\)

Ta có \(M_{AO}=M_A+16\)  (g/mol)

Nguyên tố Oxi chiếm 20% về khối lượng nên khối lượng AO là \(\dfrac{16}{20}.100\) = 80

Vậy CTHH là CuO, PTK = 80 g/mol. 

1. She revised her lessons well and could answer all the questions with confidence

2. My brother is quite good at mending electrical appliances such as TV and fridge.

3. Our neighbors have been very supportive since we moved to this village. 

4. If you still decide to do it, you should take responsibility for all the consequences.

5. I don't think obedient children are less creative than those who are naughty and stubborn.

6. The public service announcement called for volunteers to donate time to look after sick people in the local hospital. 

7. Are you going to participate in the campaign to help poor people organized by the social workers?

8. Many old people enjoy working for a charity after they retire

9. During the summer vacation, the students worked as a volunteer

10. Hai has been working in remote areas for several years and finds it useful to help the people there. 

11. Which is the most popular musical instrument in Vietnam? 

12. Hundreds of millions of viewers worldwide have watched “The Idol” program since it first launched in the UK

13. “The Kid Idol” quickly became the most popular entertainment series in America.

14. Do you see the advertisement for volunteer positions in the newspaper yesterday?

15. Volunteering can help you gain some valuable skills, whether professional or practical.