**Learning objectives**

- Represent functions of two variables with contour diagrams and tables of values
- Tell the story told by a contour diagram
- Recognize linear functions of 2 variables presented in numerical, algebraic, and graphical forms

**Before class**

- Read Hughes-Hallett 9.1 – 9.2.
- Ponder problems 9.1.1,2,4,12,16; 9.2.2,16,18,22,24.
- Consult the main points of the lesson.
- Find a cool contour diagram on the internet and post it on the Piazza forum.

**In class**

- Contour diagrams in real life together with student generated examples.
- Create formulas from linear tables and linear contour diagrams.
- Create contours from big table of values, here and here.
- Contour diagrams using R