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27 tháng 7 2018
h) Ta có: \(\left\{{}\begin{matrix}\left|x-7\right|=\left|7-x\right|\ge7-x\\\left|x+5\right|\ge x+5\end{matrix}\right.\)
\(\Rightarrow\left|7-x\right|+\left|x+5\right|\ge\left(7-x\right)+\left(x+5\right)\)
\(\Rightarrow\left|x-7\right|+\left|x+5\right|\ge12\)
\(\Rightarrow H\ge12\)
Dấu "=" xảy ra \(\Leftrightarrow\left\{{}\begin{matrix}7-x\ge0\\x+5\ge0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\le7\\x\ge-5\end{matrix}\right.\)
\(\Leftrightarrow-5\le x\le7\)
Vậy, MinH = 12 \(\Leftrightarrow-5\le x\le7\)
27 tháng 7 2018
a) Ta có: \(A=2x^2-8x+10\)
\(=2\left(x^2-4x+5\right)\)
\(=2\left(x^2-4x+2^2+1\right)\)
\(2\left[\left(x-2\right)^2+1\right]\)
Ta lại có: \(\left(x-2\right)^2\ge0\)
\(\Rightarrow2\left[\left(x-2\right)^2+1\right]\ge2\)
\(\Rightarrow A\ge2\)
Dấu bằng xảy ra \(\Leftrightarrow\left(x-2\right)^2=0\)
\(\Leftrightarrow x-2=0\)
\(\Leftrightarrow x=2\)
Vậy MinA = 2 \(\Leftrightarrow x=2\)
LS
3
16 tháng 7 2018
\(a,\)Mình làm theo kiểu lược đồ
Nhẩm nghiệm của đa thức trên ta đc : 2
Có lược đồ sau :(dòng trên ghi các hệ số)
| 1 | -2 | -6 | 12 | |
| 2 | 1 | 0 | -6 | 0 |
Ta phân tích đc thành :\(\left(x-2\right)\left(x^2-6\right)\)
\(c,x^2-5x+4\)
\(=x^2-4x-x+4\)
\(=x\left(x-4\right)-\left(x-4\right)\)
\(=\left(x-1\right)\left(x-4\right)\)
\(d,3x^2+5x+2\)
\(=3x^2+3x+2x+2\)
\(=3x\left(x+1\right)+2\left(x+1\right)\)
\(=\left(x+1\right)\left(3x+2\right)\)
\(e,x^3-x+3x^2y+3xy^2+y^3-y\)
\(=\left(x^3+y^3\right)+3xy\left(x+y\right)-\left(x+y\right)\)
\(=\left(x+y\right)\left(x^2-xy+y^2\right)+3xy\left(x+y\right)-\left(x+y\right)\)
\(=\left(x+y\right)\left[\left(x^2-xy+y^2\right)+3xy-1\right]\)
16 tháng 7 2018
\(x^3-2x^2-6x+12\)
\(=x^2.\left(x-2\right)-6\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2-6\right)\)
\(x^4-7x^2+12\)
\(=\left[\left(x^2\right)^2-2.3,5x+3,5^2\right]-0,25\)
\(=\left(x^2-3,5\right)^2-0,5^2\)
\(=\left(x^2-3,5-0,5\right)\left(x^2-3,5+0,5\right)\)
\(=\left(x^2-4\right)\left(x^2-3\right)\)
Câu c tương tự câu b
QD
11 tháng 10 2017
7: Điều gì quyết định sẽ quyết định bạn tiến bộ như thế nào? 8: Ông Ducan khuyên người học nên xem E như thế nào? 10: Hai từ quan trọng nhất cần nhớ khi học E là gì? Mối quan hệ giữa chúng là gì? 11: Ông Ducan đã sử dụng cái gì? Nó có nghĩa là gì ? 12: Đức Ducan chúng ta nói gì với chúng t
CL
13 tháng 12 2016
Choose the word that has the underlined part pronounced differently from the others.
1A. generous B. reserve C. festival D. message
2A. escape B. equipment C. excited D. emigrate
3A. appear B. annoy C. agree D. after
4. A.hoped B.raised C.died D.appeared
5A. graze B. magical C. grandmother D. rag
6A. match B. catch C. watch D. math
7A. rug B. cushion C. cupboard D. rule
8A. knife B. wife C. nice D. children
9A. happy B. try C. candy D. electricity
10A. character B. architect C. chair D. chemical
11. A. pancake B. surface C. paper D. late
12. A. wanted B. played C. learned D. returned
13. A. saucepan B. precaution C. caught D. laugh
14. A. answer B. always C. wrong D. write
15. A. injure B. knife C. kill D. sink
16. A. fun B. lunch C. run D. humor
17. A. mend B. semester C. letter D. report
18. A. shout B. loud C. group D. about
19. A. promise B.revise C. stick D. visit
20A. match B. pan C. transmit D. safety
21A. equipment B. upset C. end D. help
22A. folk B. hold C. photo D. neighbor
23A. fairy B. train C. afraid D. wait
24A. excited B. prince C. once D. escape
12 tháng 12 2016
1.B /2.D /3.D /4.A /5.A/6.C/7.D/8.D/9.B/10.C .Mình làm trước cho bạn 10 câu nhé ! Nếu bạn giỏi Toán thì giúp mình câu hỏi của mình ở trên nhé !
B
11 tháng 2 2020
III. Choose the best answer A, B, C or D.
1. If I the same problem you had as a child, I might not have succeed in life as well as you have.
A. have B. would have C. had had D. should have
2. I you sooner had someone told me you were in the hospital.
A. would have visited B. visited C. had visited D. visit
3. more help, I would call my neighbor.
A. Needed B. Should I need C. I have needed D. I should need
4. then what I know yesterday, I would have saved myself a lot of time and trouble over the years.
A. Had I known B. Did I know C. If I know D. If I would know
5. Do you think there would be less conflict in the world if all people the same language?
A. spoke B. speak C. had spoken D. will speak
6. If you can give me one good reason for your acting like this, this incident again.
A. I will never mention B. I never mention
C. will I never mention D. I don’t mention
7. If I had known you were asleep, I so much noise when I came in.
A. didn’t make B. wouldn’t have made
C. won’t make D. don’t make
8. Unless you all of my questions, I can’t do anything to help you.
A. answered B. answer C. would answer D. are answering
9. Had you told me that this was going to happen, I it.
A. would have never believed B. don’t believe
C. hadn’t believed D. can’t believe
10. If Jake to go on the trip, would you have gone?
A. doesn’t agree B. didn’t agree C. hadn’t agreed D. wouldn’t agree
11. Jane: “John went to the hospital alone”,
Katy: “If , I would have gone with him”.
A. had he told me B. he had told me
C. he has told me D. he would tell me
12. If you , I would have brought my friends over to your house yesterday to watch T.V, but I didn’t want to bother you.
A. had studied B. studied C. hadn’t studied D. didn’t study
13. Peter: “Did you need help with your Math last night?”
Mary: “If I had needed, I you".
A. would call B. called C. would have called D. will call
14. If someone into the store, smile and say, “May I help you?”
A. comes B. came C. come D. should come
15. “Here’s my phone number”.
“Thanks. I’ll give you a call if I some help tomorrow”
A. will need B. need C. would need D. needed
16. If I didn’t work for an accounting firm, I in a bank now.
A. work B. will work C. have worked D. would work
17. The death rate would decrease if hygienic conditions improved.
A. was B. is C. were D. had been
18. The education in Japan if the basic principles of education had not been taken into consideration.
A. would go down B. would have gone down
C. went down D. had gone down
19. If there , the rice fields could have been more productive.
A. had been enough water B. were enough water
C. would be enough water D. are enough water
20. The patient will not recover unless he an operation.
A. had undergone B. would undergo
C. undergoes D. was undergoing
21. If she him, she would be very happy.
A. would meet B. will meet C. met D. should meet
22. If he a thorough knowledge of English, he could have applied for this post.
A. had had B. had C. has D. has had
23. If I had enough money, I abroad to improve my English.
A. will go B. would go C. went D. should have go to
24. The bench would collapse if they on it.
A. stood B. stand C. standing D. stands
25. If it convenient, let’s go out for a drink tonight.
A. be B. is C. was D. were
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Study well❤️