Với n lẻ, đặt \(n=2k+1\); \(k\in N\)

⇒ \(n^3=\left(2k+1\right)^2\) 

\(\Leftrightarrow n^3=4k^2+4k+1\)

\(\Leftrightarrow n^3=4\left(k^2+k\right)+1\)

Vì \(4\left(k^2+k\right)⋮2\) nên \(4\left(k^2+k\right)\) chẵn

⇒ \(4\left(k^2+k\right)+1\) lẻ

⇒ \(n^3\) lẻ

1. My name's Linh. I'm 10 years old and I'm study in class 4A1.

2. My favourite colour is pastel pink.

3. My brother is tall and he is good at English.

4. We're watch TV together.

5. I would like to be an artist because painting is my favourite activity.

1. She's Vietnamese.

2. His address is 47 Queen Street.

3. He would like to be a firefighter in the future.

4. He likes helping with the cooking.

5. She likes playing piano in her free time.

My best friend is Khanh Ha. Her address is Nguyen Xien Street. Ha is short but cute. She's also kind and helpful. At the weekend, Ha often plays with her younger sister. She sometimes watchs TV. When she grew up, she want to be a singer.