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

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

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

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

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

Ta có: a<b, c<d =>a+c<b+d.

a+c<b+d

vì a với c nhỏ hơn hơn b với d

nên a + c<b+d

kb nha!

kb ko mình luôn chào đón

wow,bạn lễ phép ghê,biết là mik vi phạm nên xl cũng tốt havậy cứ kb với mik nha

3 phút 42 giây sau mik sẽ lm cho

Xin thưa bn!

~ Bn đang thi nên ko dám giúp~

Đợi 3 phút 50 giây sau mik giúp cho :>

1B 2C 3D 4D 5B

1. The Sun

2. Because of its power source.

3. It looks like an ellipse.

4. It is called fusion

5. Jupiter.

XI.

1. We might get to call her instead of writing an email.

2. It's a pity that he refused to come to the party yesterday.

3. The Earth is the third planet from the Sun and is one of the largest terrestrial planets.

4. Yesterday, she reported that she had seen a UFO in the sky the night before.

5. They thought that people would not be using snail mails in the near  future.

XII.

1. The famous scientist said that he would be introducing his latest technological invention to public the following month.

2. A foreigner journalist asked me if Twitter was popular in VN.

3. They may hold a conference call meeting this friday.

4. May I use this telephone to make some phone calls?

5. A workshop will be organized on using some useful websites for education.

\(\Rightarrow A=\frac{6n+2-5}{3n+1}=\frac{2\left(3n+1\right)}{3n+1}-\frac{5}{3n+1}\)=\(2-\frac{5}{3n+1}\)

Để A có giá trị nguyên \(\Leftrightarrow5⋮3n+1\Rightarrow3n+1\in\left\{-5;-1;1;5\right\}\)

\(\Rightarrow3n\in\left\{-6;-2;0;4\right\}\Rightarrow n\in\left\{-2;-\frac{2}{3};0;\frac{4}{3}\right\}\) Mà n \(\in Z\) 

\(\Rightarrow n\in\left\{-2;0\right\}\)

Trả lời:

Ta có: \(\frac{6n-3}{3n+1}=\frac{2\left(3n+1\right)-5}{3n+1}=\frac{2\left(3n+1\right)}{3n+1}-\frac{5}{3n+1}=2-\frac{5}{3n+1}\)

 Để A là số nguyên thì \(\frac{5}{3n+1}\)là số nguyên

=> \(5⋮3n+1\) hay \(3n+1\inƯ\left(5\right)\)\(=\left\{\pm1;\pm5\right\}\)

 Ta có bảng sau:

Vậy n \(\in\){ 0 ; -2 } thì A có giá trị nguyên

cảm ơn ạ