Với số thực a, ta định nghĩa phần nguyên của số a là số nguyên lớn nhất không vượt quá a, kí hiệu [ a ] . Dãy các số x₀ , x₁ , x₂ , ... x_n được xác định bởi công thức \(x_n=\left[\frac{n+1}{\sqrt{2}}\right]-\left[\frac{n}{\sqrt{2}}\right]\).

Hỏi trong 200 số x₀ , x₁ , x₂ , ... , x₁₉₉ có bao nhiêu số khác 0 ? ( Biết 1,41 < √2 < 1,42 ) 

IV.  Write a sentence with wish for each situation:

1. My family usually went to the pagoda on the first day of the new year. Now we don’t do that anymore.

àI wish

2. There’s a handicraft exhibition in my school tomorrow but I can’t go because I’m still sick.

à

3. I’m going to my hometown for the summer holiday. But there isn’t Internet there so it will be boring.

à

4. Sometimes I want to come back to my childhood so that I can play traditional games with my friends.

à

5. Trung really likes the new speaker model, but it is too expensive for him to afford it.

à

6. You are driving too dangerously!

à

7. I used to suffer from school-bullying because I was weak and too shy.

à

8. I feel bored as I was born and grew up in a poor countryside.

à

9. We lost the match because we didn’t try our best.

à

10. My father said that he missed his first job regretfully.

àMy father wished

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