Câu 4: Hãy cho biết hiện tượng xảy ra khi cho:

a) Kẽm vào dung dịch đồng clorua.

b) Đồng vào dung dịch bạc nitrat

c) Kẽm vào dung dịch magie clorua

d) Nhôm vào dung dịch đồng clorua.

ĐK: 2x + 1 >= 0
<=> x >= -1/2

1. Where is Maryam from?

2. How often do Lan and Maryam write to each other?

3. What was Maryam impressed by?

4. Did they visit the history museum?

Lan’s Malaysian pen pal, Razali Maryam, was staying with Lan last week. Maryam is from Kuala Lumpur. Maryam and Lan have been pen pals for over two years and they correspond at least once every two weeks, but this was their first meeting.

On Maryam's first day in Ha Noi, Lan took her to Hoan Kiem Lake. Like Kuala Lumpur, Ha Noi is a busy modern city. Maryam was really impressed by the beauty of the city and by the friendliness of its people.

Over the next few days, the girls visited Ho Chi Minh's Mausoleum, the History Museum and the Temple of Literature, as well as many beautiful parks and lakes in Ha Noi. On Friday, Maryam wanted to visit the mosque on Hang Luoc Street. Lan used to walk past the mosque on her way to primary school. However, this was Lan’s first visit. She enjoyed the peaceful atmosphere while Maryam was praying.

“I wish you had a longer vacation,” Lan said to Maryam at the end of the week.

“Yes, I wish I had more time to get to know your beautiful country better. Lan, would you like to come and visit me next summer?” Maryam asked.

“That would be great! However, it seems very difficult for me to have a trip abroad. It all depends on my parents. Anyway, we’ll keep in touch.” 

\(\sqrt{x}=15\)  

\(2\sqrt{x}=14\)

\(\sqrt{x}< \sqrt{2}\)

\(\sqrt{2x}< 4\)