Tham khảo:

I have just returned from a 1-week holiday with my friends in Da Nang and Quang Ngai. We stayed most of the time in Da Nang. Then we spent the last few nights in a very picturesque and historic place called Hoi An Old Town. We had such a relaxing time on our holiday. We enjoyed some wonderful local food. It’s really delicious. The activities we enjoyed on holiday were walking, swimming and go out at night. The water is so fresh and clean, and the temperature is just refreshing – not too hot and not too cold. We went hiking in the mountains nearly for some days, which was very good for our fitness. I really enjoyed this holiday. I loved the fresh air and the scenery, and of course the food. I will certainly be going back there another year, as I think it’s one of my favourite parts of the world.

tìm n hay chứng minh chia hết bạn

Phải cho kết quả bằng bao nhiêu mới tính được chứ bạn

VÌ 2N CHIA HẾT CHO N  MÀ 2N CỘNG 1 CHIA HẾT CHON 

VẬY 1 CHIA HẾT CHO N VÀ N BẰNG 1

bạn ơi mình ko thấy câu hỏi

Câu hỏi đâu bạn ơi :)?

đề:)?

ảnh lỗi r

Ex 3

1 C

2 B

3 B

4 B

5 B

6 A

7 A

8 A

9 B

10 A

11 C

12 C

13 C

14 A

15 A

16 C

17 A

18 C

19 A

20 B

có thấy câu hỏi đâu

thấy câu hỏi đâu

\(x^2-2\left(m-2\right)x+m^2+2m-3=0\left(1\right)\)

Để phương trình có hai nghiệm phân biệt thì Δ' > 0

\(\Rightarrow\left(m-2\right)^2-m^2-2m+3>0\Leftrightarrow m^2-4m+4-m^2-2m+3>0\Leftrightarrow-6m+7>0\Leftrightarrow m< \dfrac{7}{6}\)\)

Theo viét : \(\(\left\{{}\begin{matrix}x_1+x_2=2\left(m-2\right)\\x_1x_2=m^2+2m-3\end{matrix}\right.\)\)

Lại có :\( \dfrac{1}{x_1}+\dfrac{1}{x_2}=\dfrac{x_1+x_2}{5}\)

\(\Leftrightarrow\dfrac{x_1+x_2}{x_1x_2}=\dfrac{x_1+x_2}{5}\)

\(\Rightarrow\left(x_1+x_2\right)\left(x_1x_2\right)=5\left(x_1+x_2\right)\)

\(\Leftrightarrow\left(2m-4\right)\left(m^2+2m-3\right)=5\left(2m-4\right)\)

\(\Leftrightarrow2m^3+4m^2-6m-4m^2-8m+12=10m-20\)

\(\Leftrightarrow2m^3-24m+32=0\) \(\Leftrightarrow\left[{}\begin{matrix}m=-4\left(n\right)\\m=2\left(l\right)\end{matrix}\right.\)

Vậy \(m=-4\) thì thỏa điều kiện