Match the functions with the graphs labeled A - D. As always, you may click on the thumbnail image to produce a larger image in a new window (sometimes exactly on top of the old one). Just take your time; process of elimination will help with ones that are not obvious.

1. $f(x,y) = 3 - x^2 - y^2$
2. $f(x,y) = (x - y)^2$
3. $f(x,y) = (x^2 - y^2)^2$
4. $f(x,y) = 1/(1 + x^2 + y^2)$

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