Let n = the number of points
(x-1) + ... (x-x)
The last term will always be 0, when you reach that, stop.
ex. 1pt: 1-1=0
2pt: (2-1) + (2-2) = 1
3pt: (3-1) + (3-2) + (3-3) = 3
B.

C.

D.

please mark as brainliest.
6+1x= 7 ::::::::::::::::::::::::::::::::::
Answer:
First of all, rectangles and rectangular prisms have one foremost difference, which is their dimensions. A rectangle has two dimensions whilst a rectangular prism has three. Those dimensions include width, length, and height- but a rectangle has only width and length. Although, in comparison, they're both made from the same quadrilateral: rectangles. A "2D" rectangle has one, while a "3D" rectangle, or rectangular prism, is made of six. The rectangles that make up a rectangular prism can also be referred to as faces.