如图所示，由一些点组成形和三角形的图形，每条“边”(包括两个顶点)有n(n>1)个点，每个图形总的

Question

如图所示，由一些点组成形和三角形的图形，每条“边”(包括两个顶点)有n(n>1)个点，每个图形总的点数s是多少？当n=5,7,11时，s是多少？

Answer 1

n = 2，S = 3 = 3 x 1
n = 3，S = 6 = 3 x 2
n = 4，S = 9 = 3 x 3
n = n，S = 3 x (n-1)

n = 5，S = 3 x (5-1) = 12
n = 7，S = 3 x (7-1) = 18
n = 11，S = 3 x (11-1) = 30