KIỂm TRA THỰc HÀNH ???

KIỂM TRA TỰ LÀM 

kiểm tra thực hành lù lù kia

2. brother

3. aunt

4. uncle

5. grandma

6.grandpa

7. nephew

8.niece

9. mother

10. wife

11. cousin

2. brother 3. aunt 4. uncle 5. grandma 6.grandpa 7. nephew 8.niece 9. mother 10. wife 11. cousin

mn giusp mình ạ , mình cần gấp

f: =>(x-3)(x-1)>=0

=>x>=3 hoặc x<=1

g: =>(x-2)(x^2+3)<0

=>x-2<0

=>x<2

h: =>x+2>=0

=>x>=-2

i: =>(x-1-x+3)/(x-3)>0

=>x-3>0

=>x>3

2. Thành phần biệt lập phụ chú (Dấu gạch ngang em nhé!)

698 B

699 B

700 C

701 D

702 A

703 C

704 B

4

Đặt \(A=\dfrac{1}{\sqrt[3]{a+7b}}+\dfrac{1}{\sqrt[3]{b+7c}}+\dfrac{1}{\sqrt[3]{c+7a}}\)

\(A=\dfrac{\sqrt[3]{64}}{\sqrt[3]{8.8\left(a+7b\right)}}+\dfrac{\sqrt[3]{64}}{\sqrt[3]{8.8\left(b+7c\right)}}+\dfrac{\sqrt[3]{64}}{\sqrt[3]{8.8\left(c+7a\right)}}\)

\(\ge\dfrac{4}{\dfrac{8+8+a+7b}{3}}+\dfrac{4}{\dfrac{8+8+b+7c}{3}}+\dfrac{4}{\dfrac{8+8+c+7a}{3}}\ge\dfrac{\left(2+2+2\right)^2}{\dfrac{8+8+a+7b+8+8+b+7c+8+8+c+7a}{3}}\)

\(=\dfrac{36.3}{8\left(a+b+c\right)+48}=\dfrac{3}{2}\)

Vậy \(A_{min}=\dfrac{3}{2}\Leftrightarrow a=b=c=1\)