- #1

- 128

- 5

## Homework Statement

## The Attempt at a Solution

I don't understand what an affine function [itex]\mathbb{R}^{2}\rightarrow \mathbb{R}[/itex] expresses... I don't know if it's a coordinate function.

And i also don't understand (i'm sorry) why for any parallelogram,

**u(P) + u(R) = u(Q) + u(S)**