1. She was so lazy that she was punished by her teacher.

2. Alice started playing tennis 2 years ago.

3. My uncle is a famous stamp collector.

4. Can I meet you at between 8 am and 9 am?

5. Can you wait for me for a while?

1. She was so lazy that she was punished by her teacher.

2. Alice started playing tennis 2 years ago.

3. My uncle is a famous stamp collector.

4. Can I meet you at between 8 am and 9 am?

5. Can you wait for me for a while?

Bạn nên gõ đề bằng công thức toán (biểu tượng $\sum$ góc trái khung soạn thảo) để mọi người hiểu đề của bạn hơn nhé. Viết thế này khó đọc quá.

Lời giải:
$B=\frac{\sqrt{x}}{\sqrt{x}+1}+\frac{\sqrt{x}-4}{(\sqrt{x}-1)(\sqrt{x}+1)}$
$=\frac{\sqrt{x}(\sqrt{x}-1)+(\sqrt{x}-4)}{(\sqrt{x}-1)(\sqrt{x}+1)}$

$=\frac{x-4}{(\sqrt{x}-1)(\sqrt{x}+1)}$

Do đó:

$A:B=\frac{\sqrt{x}-2}{\sqrt{x}+1}: \frac{x-4}{(\sqrt{x}-1)(\sqrt{x}+1)}$

$=\frac{\sqrt{x}-2}{\sqrt{x}+1}.\frac{(\sqrt{x}-1)(\sqrt{x}+1)}{(\sqrt{x}-2)(\sqrt{x}+2)}$

$=\frac{\sqrt{x}-1}{\sqrt{x}+2}$

Để $A:B< \frac{1}{2}\Leftrightarrow \frac{\sqrt{x}-1}{\sqrt{x}+2}< \frac{1}{2}$

$\Leftrightarrow \frac{\sqrt{x}-1}{\sqrt{x}+2}-\frac{1}{2}<0$

$\Leftrightarrow \frac{\sqrt{x}-4}{2(\sqrt{x}+2)}<0$

$\Leftrightarrow \sqrt{x}-4<0$

$\Leftrightarrow 0\leq x< 16$

Kết hợp đkxđ suy ra $0\leq x< 16; x\neq 1$

Khi  $x=6-2\sqrt{5}=(\sqrt{5}-1)^2$ thì $\sqrt{x}=\sqrt{5}-1$
$A=\frac{\sqrt{5}-1-2}{\sqrt{5}-1+1}=\frac{5-3\sqrt{5}}{5}$

1 She could play table tennis if my friend asked 

2 Tam doesn't take part in the football match training

3 I must help my parents to work on the farm in the afternoon

4 Students should design and stick to a timetable

1 She could play table tennis if my friend asked 

2 Tam doesn't take part in the football match training

3 I must help my parents to work on the farm in the afternoon

4 Students should design and stick to a timetable

I used to keep a diary to write down special events

Stress is a problem of both adults and youngsters

Với AB là chiều cao cây, BC là bóng cây, góc tạo bởi mặt trời và mặt đất là góc C 

Ta có: \(tanC=\dfrac{AB}{BC}\)

\(\Rightarrow tanC=\dfrac{3}{2}\)

\(\Rightarrow\widehat{C}\approx56^o\)

Vậy góc tạo bởi mặt trời và mặt đất là 56^o

Ta có tan c = 3/2

C ≈56°