15. C

have someone do something: nhờ/yêu cầu ai làm gì

16. D

more and more: ngày càng...

17. B

not be cut out for something: không thích hợp với việc gì

18. D (reported speech)

19. A (tag question)

20. C

distort the truth: bóp méo sự thật

21. A

fret over: băn khoăn/lo lăng về ~

16, more and more 

17, cut out 

not be cut out for something ~ to not be the right type of person for sth

Câu 17: C

Câu 18: C

1.       Nuclear energy is … , but it is dangerous .

A.      Renewable         B. non-renewable        C. natural resource          D. fossil fuel

1.       fossil fuels are very common in our society but they … the environment .

A.      Waste          B. pollute          C. renew          D. provide

2.       All the house in our village will be … by solar energy .

A.      Frozen          B. widened          C. heated          D. heightened

3.       Several governments try to … the use of fossil fuels .

A.      waste          B. save          C. reduce          D. increase

4.       at this time next week , we … a wind turbine in our garden .

A.      will installed          B. will be installing          C. install          D. installed

5.       low energy light bulbs should be used to … electricity .

A.      convert          B. save          C. spend          D. buy

6.       it is a good idea to use … when travelling long distances .

A.      private cars          B. public transport          C. cars          D. taxis

7.       “why is it called a … source ?” – “ because it can be replaced easily and quickly ”.

A.      renewable          B. non-renewable          C. effective          D. specific

8.       we must … the amount of water our family use every day .

A.      lessen          B. narrow          C. lower          D. reduce

9.       wave energy is a source of … energy .

A.      environmental friendly           B. environmentally friendliness           

C.    environment friendly                 D. environmentally friendly

11. alternative sources of energy … developed in the near future .

A. has been           B. will be          C. is          D. was

12. she … cooking in the kitchen at 7 PM tomorrow .

A. will           B. is           C. will be           D. be

13. some new energy-saving bulbs … in the dining room .

A. will be put           B. will put be           C. will put           D. will be putting

14. what should we do to … electricity ?

A. take           B. save           C. cut           D. waste

15. the wind , the sun , and the wave are some types of … sources of energy .

A. cheap           B. costly           C. changeable           D. alternative

1.       Nuclear energy is … , but it is dangerous .

A.      Renewable         B. non-renewable        C. natural resource          D. fossil fuel

1.       fossil fuels are very common in our society but they … the environment .

A.      Waste          B. pollute          C. renew          D. provide

2.       All the house in our village will be … by solar energy .

A.      Frozen          B. widened          C. heated          D. heightened

3.       Several governments try to … the use of fossil fuels .

A.      waste          B. save          C. reduce          D. increase

4.       at this time next week , we … a wind turbine in our garden .

A.      will installed          B. will be installing          C. install          D. installed

5.       low energy light bulbs should be used to … electricity .

A.      convert          B. save          C. spend          D. buy

6.       it is a good idea to use … when travelling long distances .

A.      private cars          B. public transport          C. cars          D. taxis

7.       “why is it called a … source ?” – “ because it can be replaced easily and quickly ”.

A.      renewable          B. non-renewable          C. effective          D. specific

8.       we must … the amount of water our family use every day .

A.      lessen          B. narrow          C. lower          D. reduce

9.       wave energy is a source of … energy .

A.      environmental friendly           B. environmentally friendliness           

C.    environment friendly                 D. environmentally friendly

11. alternative sources of energy … developed in the near future .

A. has been           B. will be          C. is          D. was

12. she … cooking in the kitchen at 7 PM tomorrow .

A. will           B. is           C. will be           D. be

13. some new energy-saving bulbs … in the dining room .

A. will be put           B. will put be           C. will put           D. will be putting

14. what should we do to … electricity ?

A. take           B. save           C. cut           D. waste

15. the wind , the sun , and the wave are some types of … sources of energy .

A. cheap           B. costly           C. changeable           D. alternative

cảm ơn ạ 

12.

\(y=\sqrt{2}sin\left(2x+\dfrac{\pi}{4}\right)\le\sqrt[]{2}\)

\(\Rightarrow M=\sqrt{2}\)

13.

Pt có nghiệm khi:

\(5^2+m^2\ge\left(m+1\right)^2\)

\(\Leftrightarrow2m\le24\)

\(\Rightarrow m\le12\)

14.

\(\Leftrightarrow\left[{}\begin{matrix}cosx=1\\cosx=-\dfrac{5}{3}\left(loại\right)\end{matrix}\right.\)

\(\Leftrightarrow x=k2\pi\)

15.

\(\Leftrightarrow\left[{}\begin{matrix}tanx=-1\\tanx=3\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=-\dfrac{\pi}{4}+k\pi\\x=arctan\left(3\right)+k\pi\end{matrix}\right.\)

Đáp án A

16.

\(\dfrac{\sqrt{3}}{2}sinx-\dfrac{1}{2}cosx=\dfrac{1}{2}\)

\(\Leftrightarrow sin\left(x-\dfrac{\pi}{6}\right)=\dfrac{1}{2}\)

\(\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{\pi}{6}=\dfrac{\pi}{6}+k2\pi\\x-\dfrac{\pi}{6}=\dfrac{5\pi}{6}+k2\pi\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{\pi}{3}+k2\pi\\x=\pi+k2\pi\end{matrix}\right.\)

\(\left[{}\begin{matrix}2\pi\le\dfrac{\pi}{3}+k2\pi\le2018\pi\\2\pi\le\pi+k2\pi\le2018\pi\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}1\le k\le1008\\1\le k\le1008\end{matrix}\right.\)

Có \(1008+1008=2016\) nghiệm

Bài 4:

a) \(A=\left(x+2\right)\left(x^2-2x+4\right)-x^3+2\)

\(A=x^3+2^3-x^3+2\)

\(A=8+2\)

\(A=10\)

b) \(B=\left(x-1\right)\left(x^2+x+1\right)-\left(x+1\right)\left(x^2-x+1\right)\)

\(B=x^3-1^3-\left(x^3+1^3\right)\)

\(B=x^3-1-x^3+1\)

\(B=-2\)

c) \(C=\left(2x-y\right)\left(4x^2+2xy+y^2\right)+\left(y-3x\right)\left(y^2+3xy+9x^2\right)\)

\(C=\left(2x\right)^3-y^3+y^3-\left(3x\right)^3\)

\(C=8x^3-27x^3\)

\(C=-19x^3\)

d) \(P=\left(2x-1\right)\left(4x^2+2x+1\right)+\left(x+1\right)\left(x^2-x+1\right)\)

\(P=\left(2x\right)^3-1^3+x^3+1^3\)

\(P=8x^3-1+x^3+1\)

\(P=9x^3\)

b c b c d d b d b d