\(x^2+x+1=0\Leftrightarrow x^2+2\cdot\frac{1}{2}\cdot x+\frac{1}{4}+\frac{3}{4}=0\Leftrightarrow\left(x+\frac{1}{2}\right)^2+\frac{3}{4}=0\)
Vì   \(\left(x+\frac{1}{2}\right)^2\ge0\Rightarrow\left(x+\frac{1}{2}\right)^2+\frac{3}{4}>0\forall x\)
Vậy phương trình không có nghiệm. 
 

Nga giải đúng
Nhưng cần lời giải thuyết phục

1. Our teacher wants us to prepare our lessons carefully

Our teacher .....wants our lessons to be prepared carefully..

2. They expected me to finish my work early

They expected .......my work be finished early.....

3. Is she making big cakes for the party ?

Are ......big cakes being made for the party by her? ...............

4. The house needs cleaning

The house .......needs to be cleaned............

5. It was impossible to preserve river water in the past

River ...water was impossible to be preserved in the past .....

6. He made me stay outside yesterday

I ..was made stay outside yesterday by him ...................

7. The teacher let us go home early last week

We ...were allowed to go home early by the teacher last week..

8. He had the waiter carry the luggage home

He had ...the luggage carried home by the waiter...........

9. I got the postman to post the letter for me

I got ...the letter posted for me by the postman.......

10. Turn on the lights !

The lights ...must be turned on...........

11. They know that English is an international language

English .....is known to be an international language..................

12. Don't do that silly thing again

Don't let ....that silly thing be done again............

EX1:

1. Johnny asked his father if he could continue with his study overseas

A, "Do you think I can continue with my study overseas" said Johnny

B. "Is it possible for me to study overseas?" Johnny asked his father

C. "Can I continue with my study overseas?" Johnny said to his father

D. "Will I continue to study overseas?" Johnny said

2. She asked me ..... I liked pop music

A. when B. what C, if D, x

3. Her friend will come to see her (she hoped)

A, she hoped her friend will come to see her

B, She hoped her friend would come to see her

C. She hoped her friend comes to see her

D. She hoped her friend came to see her

4. "I'll come with you as soon as..." she replied

A. I was ready B. I am ready C. I ready D. am I ready

5. "How long....here?", asked Jane

A, you have been B, you had been C. had you been D, have you been

6, "Buy some meat in the shop" said my mother to me

A. My mother said to me to buy some meat in the shop

B. My mother told said to me to buy some meat in the shop

C. My mother told me to buy some meat in the shop

D. My mother said me to buy some meat in the shop

7. The doctor said to Peter "Don't go for a walk today"

A. The doctor said Peter not go to for a walk today

B. the doctor told Peter "Don't go for a walk today"

C. the doctor said to Peter not to go for a walk today

D. the doctor told Peter not to go for a walk today (câu trực tiếp => gián tiếp: today => that day nên không có đáp án đúng nhé)

8. I said to Nick:" Where are you going ?"

A. I asked Nick where was he going

B, I asked Nick where he was going

C. I asked Nick where is he going

D, I asked Nick where he is going

9. She asked me:" Why didn't you come here yesterday?"

A. She asked me why I hadn't gone there the day before

B. She asked me why I didn't go there the day before

C. She asked me why didn't go there the day before

D. She asked me why hadn't I gone there the day before

10. I couldn't move the piano alone, so I asked Tom...

A. giving a hand B, gave a hand C, to give a hand D, give a hand

11. The last time I saw Linda, she looked very relaxed. She explained she'd been on holiday the .... week

A, ago B, following C, next D. previous

12. "Would you like to have lunch with me on Sunday?" He said to me

A. He invited me to have lunch with him on Sunday

B. He offered me to have lunch with him on Sunday

C, He suggested me to have lunch with him on Sunday

D. He reminded me to have lunch with him on Sunday

13. "Remember to switch off when I'd finished", he said

A. He reminded me to switch off when I'd finished (I phải chuyển thành he nhé,xem lại đề hộ mình pls)

B. He offered me to switch off when I'd finished

C. He suggested me to switch off when I'd finished

D. He reminded me to switch off when I have finished

14. " Answer this letter for me, will you?" he said "And remember to keep a copy"

A, He warned me to answer that letter and reminded me to keep a copy

B. He told me to answer that letter and suggested me to keep a copy

C. He told me to answer that letter and reminded me to keep a copy

D. He suggested answering that letter and reminded me to keep a copy

15. The doctor.... him to take more exercise

A. told B, tell C, have told D, are telling

16. Judy.... going for a walk, but no one else wanted to

A. admitted B, offered C, promised D, suggested

17. Peter said he was leaving for Paris.....

A. next week B. The week previous C. following week D. the following week

18. "Will you be here tomorrow?" she asked= "Yes" I answered

A. She asked if I would be there the next day and I said that I would

B. She asked if I will be there the next day and I said that you would

C. She asked if you would be there the next day and I said that you would

D. She asked if I would be there the next day and I said that I will

19. When I rang Tessa some time last week, she said she was busy... that day ??

A, that B, the C, then D. this

20. "Could you tell me how to fet to the airport?"

A. he asked me how to get to the airport

B, He said if I could tell him the airport

C. he told me how to get to the airport

D. He asked me to tell how to get to the airport

21. They said they.... us if we needed

A. help B. helped C, would help D. had helped

22. He begged them....

A, help him B, should help him C. to help him D, help to him

23. The teacher advised us...

A. to be careful when doing these exercises

B. be careful when doing these exercises

C. careful when doing these exercises

D. are careful when doing these exercises

24. John said " You had better not lend them any money, Daisy"

A. John said Daisy not to lend them any money

B. John advised Daisy should not lend any money

C. John said to Daisy not lend them any money

D, John advised Daisy not to lend them any money

25. Claire wanted to know what time....

A. do the banks close

B, the banks closed

C. did the banks close

D, the banks would close

26. He said he would do it ....

A. yesterday

B the following day

C. the previous day

D. the day before

27. Peter asked Jane why.... the film on TV the previous night

A. didn't she watch B. hadn't she watched

C. she doesn't watch D. she hadn't watched

28. "I.... late again", she promised

A. am not B. won't be

C. wouldn't D, was not late

29. "... the door", he said

A. please open B. open pleased C. please to open D, please, opening

30. "I don't usually drink milk when ...." Mrs. Pike said

A. she was hungry

B, I was hungry

C. I am hungry

D. I will be

EX3.

1. You could make better progress if you...attended (attend) class regularly

2. If I .knew... (know) his telephone number, I'd give it to you

3. If he worked more slowly, he..wouldn't make. (not make) so many mistakes

4. I shouldn't drink that wine if I.were.. (be) you

5. If someone (give)..gave.. you a boat, what would you (do)...do.?

6. If you are kind to me, I (be).will be.. good to you

7. He (come).would come... if you waited

8. If you (ring) rang..the bell, the servant would come

9. It is (not, rain)... a lot, the rice crop wouldn't grow -> sai đề rồi

10. If today (be) were..Sunday, we wouldn't have to work

EX4:

1. Keep silent or you'll wake the baby up

-> If...you don't keep silent,you'll wake the baby up...........

2. Stop talking or you won't understand the lesson

-> If....you don't stop talking,you won't understand the lesson.......

3. I don't know her number, so I don't ring her up

-> If..I knew her number,I would ring her up...................

4. I don't know the answer, so I can't tell you

->...If I knew the answer,I could tell you......................

5. We get lost because we don't have a map

-> If....we had a map,we wouldn't get lost...............

6. Susan felt sick because she ate four cream cakes

->If...Susan hadn't eaten four cream cakes,she wouldn't have felt sick...........

7. If anyone didn't come, we would phone you at once

-> Unless...anyone came,we would phone you at once..............

8. If we had enough rain, we couldn't grow rice

-> Unless...we had enough rain,we couldn't grow rice.................

(nhưng câu 8 cũng sai đề rồi :))) phải là if we didn't have enough rain,we couldn't grow rice thì đáp án mới như trên)

đổi 2 tấn 8 tạ =2.8 tấn

\(\frac{1}{4}\)số thóc của 2 thửa ruộng là

                2.8:4=0.7 (tấn)

vậy số thóc mà bác tâm thu hoạch được ở thửa ruộng thứ 2 hơn thửa ruộng thứ nhất là 0.7 tấn

số thóc thu được ở thửa ruộng thứ 2 là 

          (2.8+0.7):2=1.75 (tấn)

                 Đ/S:1.75 tấn 

tk mk nha

1. If we continue to use fuels at the current rate, we would soon have to face a fuel crisis => will

2. If I am 10 centimeters taller, I would play basketball => were

3. If the doctors could find in the remedy, a lot of people would be saved => out

4. If she bought that house now, she ran out of money => would run

5. What you would do if you could speak French well? =>would you do

6. If tomorrow the weather will be bad, the match will be postponed => is

7. If you will see Mike today, please ask him to phone me => \(\varnothing\)

8. If I were you, I will go to the dentist's and have the tooth checked => would

9. If you hadn't left the car unlooked, it would't have be stolen =>been

10. What would happen because I pressed that red button => if

11. If the weather is fine today, we would go to the beach => will

12. If you will study harder, you will surely pass the coming exams with good results => \(\varnothing\)

13. If the weather weren't too bad, we would to go swimming => \(\varnothing\)

14. If we will reduce the speed of population growth, there will be less pressure on the earth => \(\varnothing\)

15. Unless we leave a bowl of water under the sun, it will evaporate => if

x + 500 = 9000 - 2000

x + 500 = 7000

           x = 7000 - 500

          x = 6500

a + x = 5

=> x = 5 - a

b. x - a = 3

=> x = 3 + a

c. 6 - x = a

=> x = 6 - a

k mk nha