true or false

1, there is only one midpoint for any given line segment

2, if AB+BC=AD then B lies between A and D

3, if AB+BC=AC then B is the midpoint of AC

4, If C is the midpoint of AB then AC=BC

5, if B belongs to Ox, A belongs to Oy, Ox and Oy are opposite then O is the midpoint of AB

True or false

1. we can draw many lines passing through 2 given points

2. we can draw many lines passing through 1 given point

3. we cannot draw any line passing through 3 given points

4. two different lines can only have 1 common point

5. three different lines cannot intersect at 1 point

6. we can draw 3 different lines from 3 collinear points

7. 2 parallel lines may have more than 1 common point

 true or false 

1, If Ox and Oy are opposite rays then \(\widehat{xOy=180^o}\)

2,If Ox and Oy are parallel then \(\widehat{xOy}=180^o\) or \(\widehat{xOy}=0^o\)

3, If \(\widehat{xOy}=90^o\) then \(\widehat{xOy}\) is a straight angle

4, If \(\widehat{xOy}\) +\(\widehat{yOz}=180^o\) then \(\widehat{xOy}\) and \(\widehat{yOz}\) are complementary

5, If \(\widehat{xOy}\) is larger than \(\widehat{xOz}\) then \(\widehat{xOz}\) is an acute angle

6, the lagest angle which is form by two rays is an obtuse angle

7, Two acute angles cannot be supplementary

8,\(\widehat{xOy}\) and \(\widehat{yOz}\) are adjacent

9, if \(\widehat{xOy}\) and \(\widehat{zOy}\)are supplementary then one of them must be an obtuse angle

10,if \(\widehat{xOy}\) and \(\widehat{yOz}\) are adjacent then \(\widehat{xOy}\) > \(\widehat{xOz}\)

11, If Ox lies between Oy and Oz then \(\widehat{xOy}\) and \(\widehat{yOz}\) are adjacent

true or false

1, there is only one midpoint for any given line segment

2, if AB+BC=AD then B lies between A and D

3, if AB+BC=AC then B is the midpoint of AC

4, If C is the midpoint of AB then AC=BC

5, if B belongs to Ox, A belongs to Oy, Ox and Oy are opposite then O is the midpoint of AB

True or false

1. we can draw many lines passing through 2 given points

2. we can draw many lines passing through 1 given point

3. we cannot draw any line passing through 3 given points

4. two different lines can only have 1 common point

5. three different lines cannot intersect at 1 point

6. we can draw 3 different lines from 3 collinear points

7. 2 parallel lines may have more than 1 common point

b) Trên bảng ô vuông kích thước 6x6 ấy ta viết các số tự nhiên từ 1 đến 36, mỗi số viết vào một ô một cách tuỳ ý. CMR luôn tồn tại hai ô vuông chung cạnh mà hiệu các số ghi trong chúng không nhỏ hơn 4

a) Trên một bảng ô vuông kích thước 6x6 ta viết vào mỗi ô của bảng một trong các số -1;0;1 sau đó tính tổng của các số theo từng cột, theo từng dòng và theo từng đường chéo. Chứng minh rằng luôn tồn tại hai tổng có giá trị bằng nhau