2. Stability and stability
3, 3, 3
4, greater than
5, high bottom
Second, 1,?
2、?
3、?
4、?
Fourth, because triangles are stable.
Fifth, the second road is closer, because the sum of any two sides in the triangle is greater than the third side.
6. A method for selecting * * * blue seeds. When the longest side is 15cm, there are two options: 15cm, 7cm, 13cm, 15cm, 8cm and 13cm. When the longest side is 13cm, there are several options: 13cm, 7cm and 8cm.
Project 1 "It is a historical trend that the system of weights and measures is in line with international standards