I have a data sheet which depends on x, y, and z. Therefore, the function is something like z = cx + dy, where c and d are constants and x and y may have exponents.

I don't know, however, how to graph this sort of data in excel. The surface graph seems really dissatisfactory, and does not offer me the option of seeing the equation the data makes.

My values are like this:

X--------------Y----------------Z
20-------------0-------------$1,000,232.51
15-------------5-------------$5,022,111.11
15-------------3-------------$2,333,444,34
20-------------3-------------$1,951,114.25

I need to see how X and Y affect Z, figure out the equation of this surface, and then take partial derivatives to figure out the optimal values for X and Y to maximize Z.