Hướng dẫn: A đạt GTLN khi \(\dfrac{1}{A}\) đạt GTNN

Ta có: \(x^2+2\ge0\forall x\)

\(\Rightarrow A=\dfrac{1}{x^2+2}\le\dfrac{1}{2}\forall x\)

Vậy GTLN của A là 1/2

=> A

Câu 2: B đạt GTLN khi và chỉ khi x² đạt giá trị nhỏ nhất

⇔ x²=0 ⇒B = 10 - 0= 0 

  Chọn đáp án B nhe

Câu 3: Có A= 4x - 2x²= (-2x² + 4x - 1) + 1=\(-2\left(x^2-2x+1\right)+1\)

⇔ A= \(-2\left(x-1\right)^2+1\le1\)

Chọn đáp án B nha

A

có bạn giúp r nha bạn

1. English is more interesting than music.

2. Today they are not as happy as they were yesterday.

3. Ha Noi is not as small as Hai Duong.

4. Mai's sister is not as pretty as her.

6. You have got more money than me.

7. Art is not as difficult as French.

8. Nam's father is more careful than him.

9. No one in our town is as rich as Mr Ron.

10. He is the most intelligent in my class.

11. Everest is the highest mountain in the world.

12. Minh is the fattest person in my group.

13. I can't swim as far as Jan.

14B 15C 16A 17C 18B 19C 20B

bạn có thể chụp thẳng đc hong?????

a) \(\dfrac{1}{4}-3\left(\dfrac{1}{12}+\dfrac{3}{8}\right)=\dfrac{1}{4}-\dfrac{1}{4}-\dfrac{9}{8}=-\dfrac{9}{8}\)

b) \(\left(-\dfrac{2}{3}+\dfrac{3}{5}\right):\dfrac{1}{50}-30=\left(-\dfrac{2}{3}+\dfrac{3}{5}\right).50-30=-\dfrac{100}{3}+30-30=-\dfrac{100}{3}\)

Câu 5:

Điện trở tương đương:

R₂₃ = R₂ + R₃ = 6 + 4 = 10\(\Omega\)

R₂₃₄ = (R₂₃.R₄) : (R₂₃ + R₄) = (10.10) : (10 + 10) = 5Ω

R_tđ = R₁ + R₂₃₄ = 2 + 5 = 7Ω

Tham khảo:

Câu 6:

a: góc AQE=góc AKE=90 độ

=>AQKE nội tiếp

=>góc KQE=góc KAE=góc BCE
b: góc EAC=góc EBC

góc EBC=góc DKE

=>góc EBC=góc DKE

=>góc EAN=góc EKN

=>AKEN nội tiếp

=>góc ANE+góc AKE=180 độ

=>góc ANE=90 độ

DNCE có góc ENC=góc EDC=90 độ

nên DNEC nội tiếp

+>góc E1=góc C1

mà góc C1=góc A1=góc E2

nên góc E1=góc E2

=>ΔQKE đồng dạng với ΔDNE

=>EN*QK=ND*EQ