\(R_{tđ}=\dfrac{R_1\cdot R_2}{R_1+R_2}=\dfrac{24\cdot12}{24+12}=8\Omega\)

\(I=\dfrac{U}{R}=\dfrac{12}{8}=1,5A\)

\(P=\dfrac{U^2}{R}=\dfrac{12^2}{8}=18W\)

\(Q_{tỏa1}=A_1=U_1\cdot I_1\cdot t=12\cdot\dfrac{12}{24}\cdot1\cdot3600=21600J\)

\(Q_{tỏa2}=A_2=U_2\cdot I_2\cdot t=12\cdot\dfrac{12}{12}\cdot1\cdot3600=43200J\)

After many pressure in life, one individual always has their own home to come back called country and Vietnam is my beautiful country. Although it is small, it has several beautiful landscape and tourist attraction. I can list out: Ha Long bay, Phong Nha cave, Nha Trang beach, Hoi An old town and so on. VN is famous for its green field, peaceful village and friendly people. Vietnamese are kind, humble, honest as well as hospitable. Besides, there are other good personalities such as: brave, patience, diligence. Country is an abstract definition including all of the most familiar things belonged to one spirit. Country plays a crucial role in nurturing one spirit and lifestyle. Each individual is a mirror reflects country’s tradition, culture, habits and customs. Specifically, there are several customs in different areas as VN has 54 ethnic groups. Each group has their own national character, which distinguish them from others. Therefore, protecting and preserving national character are Vietnamese’s duty from very old days. If there is a chance to visit our country, don’t hesitate to catch it cause VN maintains a lot of undiscovered mystery. I love VN and people here so much and I hope foreign tourists will visit my country one future day.

There have been a lot of changes in my village in recent years.
Firstly, we are better equipped with many modern electrical equipment such as TVs, refrigerators, etc. Secondly, we have built hospitals, schools, buildings and nearby factories, helping life. Our local better.
In parular, young people may have more opportunities to get a high paying job.
For these reasons, we really feel happy about the changes.
However, these changes also have some negative effects.
Plants pollute the air and water. There are more people, more traffic jams and accidents, less space and less fresh air. etc. I can balance both positive and negative impacts to have a beautiful life.

3²ˣ⁺¹ - 20 = 7

3²ˣ⁺¹ = 7 + 20

3²ˣ⁺¹ = 27

3²ˣ⁺¹ = 3³

2x + 1 = 3

2x = 3 - 1

2x = 2

x = 2 : 2

x = 1

Câu 4.

a)\(0,375A=0,375\cdot1000=375mA\)

b)\(200mA=\dfrac{200}{1000}=0,2A\)

c)\(1,25V=1,25\cdot10^{-6}MV\)

d)\(500kV=500000V\)

Câu 7.

Hai đèn mắc nối tiếp.

Khi đó dòng điện qua các đèn và toàn mạch là như nhau.\(\Rightarrow I_{mạch}=I_{Đ1}=I_{Đ2}\)

Hiệu điện thế qua đoạn mạch là:

\(U_{mạch}=U_{Đ1}+U_{Đ2}=4,8+2,5=7,3V\)

Mờ quá ạ

1) Áp dụng định lí Pytago vào ΔABC vuông tại A, ta được:

\(BC^2=AB^2+AC^2\)

\(\Leftrightarrow BC^2=6^2+8^2=100\)

hay BC=10(cm)

Áp dụng hệ thức lượng trong tam giác vuông vào ΔABC vuông tại A có AH là đường cao ứng với cạnh huyền BC, ta được:

\(AH\cdot BC=AB\cdot AC\)

\(\Leftrightarrow AH\cdot10=6\cdot8=48\)

hay AH=4,8(cm)

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