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\(\left(11-x\right)+\left(14-x\right)+...+\left(146-x\right)=3473\)

Tổng trên có 46 số hạng

⇒ \(\left(11+14+..+146\right)+46x=3473\)

⇔ \(3611+46x=3473\)

⇔ \(46x=-138\)

⇔ \(x=-3\)

x = -3

giúp với huhuhu

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quên òi

1, C

2,A

3,D

4,C

II

1,B

2,C

3,B

4,A

5,B

6,D

7,sai đề, good

8,B

Question I

1 C

2 A

3 D

4 C

Question II

1 B

2 C

3 B

4 A

5 B

6 D

7 A

8 B

Question III

1 A

2 B

3 C

4 C

Question IV

1 plays

2 goes

3 goes

4 listens

5 watches

6 plays

7 goes

8 plays

QuestionV

1 He stayed at home because he was sick

2 It was very cold but they went swimming

3 We can go camping or we can go for a picnic

4 He didn't wash his hands so he had a stomachache

Question VI

1  They give away warm clothes to homeless people in Ha Noi.

2 We haven't had a vacation since last year

Queston VII

1 riding

2 went

3 have lived

4 take

III

1a

2b

3c

4c

IV

Rick has a lot of hobbies. He (1) ..plays. chess at school and he also (2) ..goes. skating. After dinner, he (3) .goes... for work and he (4) ...listens.. to music every evening in his room. John loves sports. He (5) ..does... athletics at school, and he (6) ...plays... football after school. On Saturday, John and his friends (7) ....go..  swiming. On sundays, they (8) ..play... basketball 

1 C

2 C

III

1 C

2 D

3 B

4 C

11 C

13 B

6,C

7,C

8,C

9,B

10,B

11,C

12,C

13,B

9C 10D 11C 12B 13A 14B 15B 16B 17A 18B 19D 20B 21B 22D 23C 24D 25C 26A 

27. It is 300km from Ho Chi Minh city to Phu Quoc Island.

28. Traffic rules should be obeyed strictly by road users.

29. If you are not careful, you’ll hurt yourself.

30. They will be learning English this time tomorrow.

Đặt \(cosx-sinx=t\Rightarrow-\sqrt{2}\le t\le\sqrt{2}\)

\(t^2=1-2sinx.cosx\Rightarrow sinx.cosx=\dfrac{1-t^2}{2}\)

Pt trở thành:

\(t\left(1+\dfrac{1-t^2}{2}\right)+1=0\)

\(\Leftrightarrow t^3-3t-2=0\)

\(\Leftrightarrow\left(t-2\right)\left(t+1\right)^2=0\Rightarrow\left[{}\begin{matrix}t=2\left(loại\right)\\t=-1\end{matrix}\right.\)

\(\Rightarrow cosx-sinx=-1\)

\(\Leftrightarrow\sqrt[]{2}cos\left(x+\dfrac{\pi}{4}\right)=-1\)

\(\Leftrightarrow cos\left(x+\dfrac{\pi}{4}\right)=-\dfrac{\sqrt{2}}{2}\)

\(\Leftrightarrow cos\left(x+\dfrac{\pi}{4}\right)=cos\left(\dfrac{3\pi}{4}\right)\)

\(\Leftrightarrow...\)