b, Do x; y thuộc Z => 4x + 4; 3y + 3 thuộc Z
Mà (4x + 4)(3y + 3) = 36
=> 4x + 4; 3y + 3 thuộc Ư(36)
Ta thấy 4x + 4 chẵn và chia hết cho 4 => 4x + 4 = -4; 4; -12; 12; -36; 36
Ta có bảng :
| 4x + 4 | -4 | 4 | -12 | 12 | -36 | 36 |
| 3y + 3 | -9 | 9 | -3 | 3 | -1 | 1 |
| x | -2 | 0 | -4 | 2 | -10 | 8 |
| y | -4 | 2 | -2 | 0 | -4/3 | -2/3 |
Vậy các cặp (x; y) thỏa mãn là : (-2; -4); (0; 2); (-4; -2); (2; 0)
@hoàng thị anh
Do Ot là tia phân giác của \(\widehat{xOy}\) => \(\widehat{tOy}\) \(=\dfrac{1}{2}\widehat{xOy}\)
Lại do Ot' là tia phân giác của \(\widehat{x'Oy}\) => \(\widehat{t'Oy}\) = \(\dfrac{1}{2}\widehat{x'Oy}\)
=> \(\widehat{tOy}+\widehat{t'Oy}=\dfrac{1}{2}\widehat{xOy}+\dfrac{1}{2}\widehat{x'Oy}\)
=> \(\widehat{tOt'}\) = \(\dfrac{1}{2}\left(\widehat{xOy}+\widehat{x'Oy}\right)\)
=> \(\widehat{tOt'}\) = \(\dfrac{1}{2}\).180o
=> \(\widehat{tOt'}\) = 90o
Điều đó chứng tỏ Ot vuông góc với Ot'
@Trà My Phạm
1, It's ten past eleven.
=> What time is it ?
2, We are in class 6B.
=> Which class are you in ?
3, They have two children.
=> How many children do you have ?
4, Jim's flat is on the four floor.
=> Which floor is Jim's flat on ?
5, My brother is in grade twelve.
=> Which grade is your brother in ?
6, She has lunch at eleven thirty.
=> What time does she have lunch ?
7, There is one boy in our class.
=> How many boys are there in your class ?
8, That is our teacher.
=> Who is that ?
9, There are pencils.
=> What are those ?
10, Mr. Quang lives in the country.
=> Where does Mr.Quang live ?
@Có tên