On mới trả lời đc câu hỏi của bạn chứ.

1. on

2. to - for

3. of

4. in

5. in/ with

6. in

7. at

8. in

9. in

10. on - at

11. for

12. on

13. at - at

14. at

15. of

16. to

17. in

18. on

19. about

20. of

Các bn thấy đúng không

1. Lan'll have a party on Friday evening.

2. Would you to come in my house at lunch?

3. She takes care of  her family.

4. She works in a local supermarket.

5. My mother works on the field  With my father.

6. Does your father work in Hanoi?

7. David is good at Math.

8. What do you do in your free time?

9. Are you interested at. sports?.

10. There's a good film at. the moment.

11. Thanks for . your letter.

12. I'll see my mom and dad in . their farm.

13. We have to work hard .at home and at .. school

14. We'll visit her at. Christmas.

15. Are you tired to . watching TV?

16. She often brings them to. school.

17. He works in a factory.

18. We always go to Ha Long Bay .at.. vacation.

19. Tell me more .in . your family.

20. Can you send me a photo with . your family?

- Mk chắc z thôi nhé <3

a)4n²-3n-1 chia hết cho 4n-1

<=>4n²-n-2n-1 chia hết cho 4n-1

<=>n(4n-1)-(2n+1) chia hết cho 4n-1

<=>2n+1 chia hết cho 4n-1

<=>2(2n+1) chia hết cho 4n-1

<=>4n-1+3 chia hết cho 4n-1

<=>3 chia hết cho 4n-1

=>4n-1 thuộc Ư(3)

=>Ư(3)={-1;1;-3;3}

Ta có bảng sau:

Vậy n thuộc {0;1}

b)4n²-3n-1 chia hết cho n-1

<=>4n²-4n+n-1 chia hết cho n-1

<=>4n(n-1)+n-1 chia hết cho n-1

<=>(4n+1)(n-1) chia hết cho n-1

<=>n thuộc N với mọi gtrị

P/s: "chia hết cho" thì viết kí hiệu vô

Is that T :))

admin là con chó

sao chửi admin là chó

a.\(2n^2-3n+1=2n\times\left(n-1\right)-\left(n-1\right)=\left(2n-1\right)\times\left(n-1\right)\Rightarrow2n-1⋮n-1\)

\(\Rightarrow2\left(n-1\right)+1⋮n-1\Rightarrow1⋮n-1\Rightarrow n-1\inƯ\left(1\right)=\left\{1\right\}\Rightarrow n=2\)

b.Tách tương tự nha

\(2n^2-3n+1=\left(2n^2-2n\right)-n+1=2n\left(n-1\right)-n+1\)\(\Rightarrow-n+1⋮n-1\Rightarrow-\left(n-1\right)⋮n-1\)

vậy với mọi x thuộc N đều t/m

b) tương tự nha