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MN XONG CÂU NÀO THÌ CỨ GỬI LUÔN CHO MIK CÂU ĐÓ NHA;-;

MIK CÒN CHÉP KỊP

:(((((((((((((( NHANHH NHANH GIÚP MIK Ạ

Câu 1:

\(a,\dfrac{x}{4}=\dfrac{y}{7}=\dfrac{x-y}{4-7}=\dfrac{-15}{-3}=5\\ \Rightarrow\left\{{}\begin{matrix}x=20\\y=35\end{matrix}\right.\\ b,\dfrac{x}{3}=\dfrac{y}{5}=\dfrac{x+y}{3+5}=\dfrac{-32}{8}=-4\\ \Rightarrow\left\{{}\begin{matrix}x=-12\\y=-20\end{matrix}\right.\\ c,\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{5}=\dfrac{x+y+z}{2+3+5}=\dfrac{-90}{10}=-9\\ \Rightarrow\left\{{}\begin{matrix}x=-18\\y=-27\\z=-45\end{matrix}\right.\\ d,\dfrac{x}{4}=\dfrac{y}{2}=\dfrac{z}{7}=\dfrac{2x-4y+3z}{8-8+21}=\dfrac{42}{21}=2\\ \Rightarrow\left\{{}\begin{matrix}x=8\\y=4\\z=14\end{matrix}\right.\)

\(e,\dfrac{x}{5}=\dfrac{y}{6}=\dfrac{z}{7}=\dfrac{z-x}{7-5}=\dfrac{30}{2}=15\\ \Rightarrow\left\{{}\begin{matrix}x=75\\y=90\\z=105\end{matrix}\right.\\ f,\Rightarrow\dfrac{x}{3}=\dfrac{y}{5};\dfrac{x}{4}=\dfrac{z}{3}\Rightarrow\dfrac{x}{12}=\dfrac{y}{20}=\dfrac{z}{9}=\dfrac{x-y-z}{12-20-9}=\dfrac{-68}{-17}=4\\ \Rightarrow\left\{{}\begin{matrix}x=48\\y=80\\z=36\end{matrix}\right.\\ g,\Rightarrow\dfrac{x}{6}=\dfrac{y}{4}=\dfrac{z}{3}=\dfrac{x+y+z}{6+4+3}=\dfrac{65}{13}=5\\ \Rightarrow\left\{{}\begin{matrix}x=30\\y=20\\z=15\end{matrix}\right.\\ h,\Rightarrow\dfrac{x}{4}=\dfrac{y}{6};\dfrac{y}{5}=\dfrac{z}{8}\Rightarrow\dfrac{x}{20}=\dfrac{y}{30}=\dfrac{z}{48}=\dfrac{5x-3y-3z}{100-90-144}=\dfrac{-536}{-134}=4\\ \Rightarrow\left\{{}\begin{matrix}x=80\\y=120\\z=192\end{matrix}\right.\)

B D A C

1-B

2-D

3-A

4-C

1B

2D

3A

4C

III) Choose the correct option A, B, C or D to complete the sentences.

1. Nuclear energy can provide electricity for the world needs, but it is ……………..

        A. cheap                    B. unlimited               C. dangerous              D. safe

2. In the future most people will travel  …………….. flying train.

        A. in                          B. to                          C. on                         D. at

3. Do you think we …………….. driverless car in the future?

        A. use                        B. to use                    C. will use                  D. have used

4. Linda used to …………….. morning exercise when she got up early.

        A. did                        B. does                      C. doing                     D. do

5. We were …………….. with the latest film of that director.

        A. satisfied                  B. satisfatort               C. satisfying               D. satisfy

6. The play was so boring. …………….. , An saw it from beginning to end.

        A. In spite of              B. Despite                  C. However               D. Although

7. We found the plot of the film …………….. .

        A. bored                    B. boring                   C. interesred               D. acting

8. My father liked the …………….. of that singer.

        A. perform                 B. performer              C. performance          D. performing

9. I …………….. go on foot when I was in primary school.

        A. used to                  B. break                     C. can                        D. may

10. We didn’t find it funny ……………….. it was a comedy.

        A. but                        B. although                C. despite                   D. in spite of

11. Drivers have to ……………….. your seatbelt whenever they drive.

        A. tie                          B. fasten                     C. put on                   D. put

12. At 7.00 tomorrow, you …………….. to school.

        A . will be cycled          B. will cycle                 C. will be cycling  D. cycle  

13. Solar energy …………….. by many countries in the world in the future.

        A. will use                    B. will be used           C. will be using D. use

14. At this time tomorrow, I …………….. an interview.

        A. will be having       B. will have               C. had                        D. have

15. A  …………….. is  a film that shows real life events stories.

        A. horror                    B. comedy                 C. action          D. documentary

16. We should …………….. low energy light bulbs.

        A. use                        B. using                     C. used                      D. to use

17. The wind turns …………….. to make electricity.

        A. fans                       B. leaves                    C. turbines                 D. kites

18. We …………….. an English test tomorrow.

        A. will have               B. have                      C. will be having        D. had

19. Solar energy will ……………..  to solve the problem of energy shortage.

        A. use                        B. be used                  C. used                      D. using

20. The sun and the wind are other …………….. sources of energy.

        A. alternative              B. renewable              C. non-renewable       D. nuclear

21.The boys ………. home because they are planning to visit the hydro power station.

        A. have not come       B. do not come          C. will not be coming D. is not coming

22. They …………….. a test at 8.00 tomorrow; we don’t want to disturb them.

        A. will be having         B. will have              C. have                            D. had

23.You should turn  …………….. the lights when leaving the rooms.

        A. on                         B. off                         C. right                      D. left

24. Which of the following is NOT renewable source of energy?

        A. wind                     B. coal                       C. hydro                    D. solar

25. This is Linda’s hat, and those shoes are ………………

        A. our                        B. hers                       C. her                         D. their

26. A sky safety system can help cars to ………………… traffic jams and crashes.

        A. use                        B. have                      C. prevent                  D. take

27. The white cat is Helen’s, and the black cat is …………………

        A. I                            B. my                         C. mine                      D. of mine

28. The festival ………………… every year at the end of August.

        A. occur                     B. takes place             C. takes                      D. held

1 C

2 B

3 B

4 C

5 B

6 B

7 D

8 B

9 A

10 B

Bài 4

1 for

2 of

3 about

\(\dfrac{3a-2b}{5}=\dfrac{2c-5a}{3}=\dfrac{5b-3c}{2}=\dfrac{6c-15a}{9}=\dfrac{10b-6c}{4}=\dfrac{6c-15a+10b-6c}{9+4}=\dfrac{10b-15a}{13}\)

\(\Rightarrow\dfrac{3a-2b}{5}=\dfrac{10b-15a}{13}\Rightarrow39a-26b=50b-75a\)

\(\Rightarrow114a=76b\Rightarrow b=\dfrac{3}{2}a\)

Tương tự:

\(\dfrac{2c-5a}{3}=\dfrac{3a-2b}{5}=\dfrac{5b-3c}{2}=\dfrac{15a-10b}{25}=\dfrac{10b-6c}{4}=\dfrac{15a-10b+10b-6c}{25+4}=\dfrac{15a-6c}{29}\)

\(\Rightarrow\dfrac{2c-5a}{3}=\dfrac{15a-6c}{29}\Rightarrow58c-145a=45a-18c\)

\(\Rightarrow76c=190a\Rightarrow c=\dfrac{5}{2}a\)

Thế vào \(a^2+275=bc\)

\(\Rightarrow a^2+275=\left(\dfrac{3}{2}a\right).\left(\dfrac{5}{2}a\right)=\dfrac{15}{4}a^2\)

\(\Rightarrow\dfrac{11}{4}a^2=275\Rightarrow a^2=100\Rightarrow a=\pm10\)

- Với \(a=10\Rightarrow b=\dfrac{3}{2}a=15\) ; \(c=\dfrac{5}{2}a=25\)

- Với \(a=-10\Rightarrow b=-15;c=-25\)

a) Ta có: \(P\left(x\right)=7x^3+3x^4-x^2+5x^2-6x^3-2x^4+2017-x^3\)

\(=x^4+4x^2+2017\)

b) Bậc của P(x) là 4

c) Các hệ số của P(x) là 1;4;2017

Hệ số cao nhất là 4

Hệ số tự do là 2017

d) \(P\left(0\right)=0^4+4\cdot0^2+2017=2017\)

\(P\left(1\right)=1^4+4\cdot1^2+2017=1+4+2017=2022\)

\(P\left(-1\right)=\left(-1\right)^4+4\cdot\left(-1\right)^2+2017=1+4+2017=2022\)

e) \(P\left(-a\right)=\left(-a\right)^4+4\cdot\left(-a\right)^2+2017=a^4+4a^2+2017\)

\(P\left(a\right)=a^4+4a^2+2017\)

Do đó: P(-a)=P(a)

lỗi ảnh

OK