K
Khách

Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.

26 tháng 1 2017

Dịch: Giá trị lớn nhất của A=6/2(x-3)2+3

Giải

Vì có mũ 2 nên x-3 lớn hơn hoặc bằng 0

Ta có khi mẫu số càng nhỏ p/số càng lớn.Vậy 2(x-3)2+3 nhỏ nhất (lớn hơn 0)=>2(x-3)2+3=1

=>Giá trị lớn nhất của A=6/1=6

Sai sửa hộ mình nhé

30 tháng 10 2016

\(\frac{x^2+15}{x^2+3}\)

\(=\frac{x^2+3+12}{x^2+3}\)

\(=\frac{x^2+3}{x^2+3}+\frac{12}{x^2+3}\)

\(=1+\frac{12}{x^2+3}\)

\(x^2\ge0\)

\(x^2+3\ge3\)

\(\frac{12}{x^2+3}\le4\)

\(1+\frac{12}{x^2+3}\le5\)

ĐS: 5

Exercise 2: Give the correct form of the verbs in brackets.1. The news about Mr Hogan (be) ___________surprising.2. Fifty minutes (be)___________the maximum length of the time allowed for the exam.3. Many people in the world (not have) ___________enough food to eat.4. The poor (need)___________ help from the community.5. Listening to loud music at rock concerts  (cause)_______ hearing loss in some teenagers these days.6. There (be) ___________a lot of sheep in the field.7. Ten miles (be)...
Đọc tiếp

Exercise 2: Give the correct form of the verbs in brackets.

1. The news about Mr Hogan (be) ___________surprising.

2. Fifty minutes (be)___________the maximum length of the time allowed for the exam.

3. Many people in the world (not have) ___________enough food to eat.

4. The poor (need)___________ help from the community.

5. Listening to loud music at rock concerts  (cause)_______ hearing loss in some teenagers these days.

6. There (be) ___________a lot of sheep in the field.

7. Ten miles (be) ___________ too far to walk.

8. Not only John but also his friends (want) ___________ to buy this race horse.

9. A number of students (recently participate) ___________ in intensive language programs abroad.

10. Sarah, along with 20 students, (plan) ___________a party now.

11. The number of students who (withdraw) ___________from class since the term began

      (be) ___________quite high.

12. There (be) at least one window in every room.

13. A lot of students in my class (speak) ___________ and (undrstand) ___________ Spanish.

14. The trousers Lan’s bought (not, go) ___________ best with her shirt.

15. The information she gave me (be not) ___________valuable.

16. The number of days in a week (be) ___________seven.

17. Either you or he (have) ___________to do the task.

18. Two years without a job (be) ___________too long to be.

19. Every girl and boy (be) ___________required to have certain immunizations before enrolling in public school.

20. Neither of John’s parents (be)___________ English.

1
5 tháng 11 2021

1 is

2 is

3 don't have

4 need

5 causes

6 are

7 is

8 want

9 have recently participated

10 is planning

11 withdraw - to be

12 is

13 speak - understand

14 don't go

15 wasn't

16 is

17 has

18 is

19 is

20 is

a: \(=-3\left(x^2+3x+\dfrac{25}{3}\right)\)

\(=-3\left(x^2+3x+\dfrac{9}{4}+\dfrac{73}{12}\right)\)

\(=-3\left(x+\dfrac{3}{2}\right)^2-\dfrac{73}{4}< =-\dfrac{73}{4}\)

Dấu '=' xảy ra khi x=-3/2

b: \(=-\left(x^2-x+\dfrac{1}{4}-\dfrac{1}{4}\right)=-\left(x-\dfrac{1}{2}\right)^2+\dfrac{1}{4}< =\dfrac{1}{4}\)

Dấu '=' xảy ra khi x=1/2

c: \(=-\left(x^2-7x-12\right)\)

\(=-\left(x^2-7x+\dfrac{49}{4}-\dfrac{97}{4}\right)\)

\(=-\left(x-\dfrac{7}{2}\right)^2+\dfrac{97}{4}< =\dfrac{97}{4}\)

Dấu '=' xảy ra khi x=7/2

NV
16 tháng 7 2020

Let \(A=x^2+2y^2+2x-4\)

From condition, we have: \(y^2=7-x^2\)

Therefore: \(A=x^2+2\left(7-x^2\right)+2x-4\)

\(\Rightarrow A=-x^2+2x+10=-\left(x-1\right)^2+11\le11\)

\(\Rightarrow A_{max}=11\) when \(\left\{{}\begin{matrix}x=1\\y^2=6\end{matrix}\right.\)

15 tháng 2 2017

Coi 2 cạnh của hình chữ nhật là a và b, a+b=10.Sử dụng BĐT Cauchy: \(ab\le\frac{a^2+b^2}{2}\)Dấu "=" xảy ra khi a=b=5 tức là max(ab)=25