B = x² + 5x + 1
= x² + 2 . x . 2,5 + 6,25 - 5,25
= (x + 2,5)² - 5,25
Do (x + 2,5)² ≥ 0 với mọi x
=> B = (x + 2,5)² - 5,25 ≥ -5,25
Vậy minB = -5,25 khi (x + 2,5)² = 0
=> x + 2,5 = 0
=> x = -2,5
$B=x^2+5x+1$$B=x^2+2.x.\dfrac{5}{2}+\dfrac{25}{4}-\dfrac{21}{4}$$B=(x+\dfrac{5}{2})^2-\dfrac{21}{4}$$(x+\dfrac{5}{2})^2≥0∀x$$⇒(x+\dfrac{5}{2})^2-\dfrac{21}{4}≥\dfrac{-21}{4}$Dấu $"="$ xảy ra khi
$x+\dfrac{5}{2}=0$$⇔x=\dfrac{-5}{2}$Vậy $B_{min}=\dfrac{-21}{4}⇔x=\dfrac{-5}{2}$
Tính nhanh: 35^2 + 40.35 +20^2 - 45^2
Tuổi trung bình của bố, mẹ và Nam là 27 tuổi..tuổi trung bình của bố và Nam là 23 tuổi. em hãy tính tuổi của mẹ Nam
Bạn nào đó cho mình xin ý trong bài " Trong lòng mẹ " ( khi gặp lại mẹ ) với ah! TKS
x(5x – 3) – x2 (x – 1) + x(x2 – 6x) – 10 + 3x Giải hộ ạ
Choose the best answer Mình cần gấp
I. Choose one word whose underlined part is pronounced differently from the others. 1. A. knife B. injure C. scissors D. sink 2. A. precaution B. cause C. because D. aunt 3. A. cover B. movie C. above D. oven 4. A. reach B. beneath C. near D. bead 5. A. chemical B. chore C. kitchen D. children II. Choose from the four options given one best answer to complete each sentence. 1. What does your friend look_________? A. likes B. like C. likely D. to like 2. Is she going to________ you this summer? A. visit B. visits C. visted D. visiting 3. Why did Romeo and Juliet kill___________? A. they B. them C. themselves D. themself 4. Why do we have to put all dangerous objects out of___________. A. children reach B. reach chidren C. children reaching D. children’s reach
giúp chiều phải nộp nha , hứa cho hay nhất
B=x mũ 2 +5x+7 Tìm giá trị nhỏ nhất Trả lời đúng +nhanh cko 5 sao +1 cảm ơn
viết mỗi tập hợp sau bằng cách liệt kê các hần tử của nó {x∈N| ( x^2 -10x +21 ).(x^3 -x)=0
1. “Why don’t you put better lock on the door, Barbara”? said John => John suggested…………………………………………………………………………………….. 2. Although his both legs were broken in the crash, he managed to get out of the car before it exploded. => Despite his………………………………………………………………………………………….. 3. I haven’t eaten this kind of food before. => This is the first……………………………………………………………………………….. 4. The architect has drawn plans for an extension to the house. => Plans………………………………………………………………………………………………… 5. It isn’t necessary for you to finish by Saturday => You……………………………………………………………………………………… 6. “How many survivors are there?”, asked the journalist. => The journalist wanted to know……………………………………………………………… 7. It was such rotten meat that it had to be thrown away. => The meat was……………………………………………………….. 8. It is essential that Professor Van Helsing is met at the airport. => Professor Van Helsing…………………………………………………………………….. 9. You can’t visit the USA unless you have a visa. => If you……………………………………………………….. 10. “Can I borrow your typewriter, Janet”? asked Peter. => Peter asked if…………………………………………………………….. 11. She started working as a secretary five years ago. => She has…………………………………………………………………… 12. She knows a lot more about it than I do. => I don’t know……………………………………………………………………. 13. My French friend finds driving on the left difficult. => My French friend isn’t…………………………………………………………………. 14. They think the owner of the house is abroad. => The owner…………………………………………………………………………. 15. We didn’t go on holiday because we did not have enough money. => If we…………………………………………………………………………………….
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