[Not to be turned in]
 In class, we talked more about how to use $x$ and $y$traces to understand the graph of a function $f\colon\R^2\to\R$.
Use these techniques to sketch the graphs of the following:
 $f(x,y) = 1x^2y^2$
 $f(x,y) = (xy)^3$
 $f(x,y) = x + y$
 In class, we discussed how a level set is the collection of points in the domain that cause a function to produce a specific (fixed) output.
Consider the function $f(x,y)=xy$ that we graphed in class today.
 Sketch the level set for $f$ that produces the value $0$?
 Sketch the level set for $f$ that produces the value $1$?
 Sketch the level set for $f$ that produces the value $1$?
 Finish the WeBWorK assignment.

