\(\text{ĐK: }x\ge9\)

Côsi: \(x=\left(x-9\right)+9\ge2\sqrt{9\left(x-9\right)}=6\sqrt{x-9}\)

\(\Rightarrow S=\frac{\sqrt{x-9}}{5x}\le\frac{\sqrt{x-9}}{5.6\sqrt{x-9}}=\frac{1}{30}.\)

Đẳng thức xảy ra khi \(x-9=9\Leftrightarrow x=18.\)

Bài 2 :

1.goes

2. will not go

3. are

4. don't enjoy

5.will see

6.lives

7.will meet

8.goes

9 will not come

10. Will she go

TÊN : Chi
Lớp 8A
https://hoc24.vn/vip/1918547621753840

1. Although this village is famous for its silk products, there is not many people know how to weave.

2. Many people love going to this park because it's wide and fresh.

3. Since the crafts remind people of a specific region, foreign tourists often buy traditional handicrafts.

4. Moc Chau is a popular tourist attraction when the spring is coming.

5. This weekend we're going to the cinema in order that we can see a great film.

bai mấy ạ

1.We have been taught by Mr Smith for 2 years

2. A great deal of tea is drank in england

3.English is spoken all over the world

4. Her dog is often taken for a walk