1. Consider the function f(x, y) = (x 1) + 3(y 2) +5. (a) Sketch a graph of this function or use a tool like GeoGebra3D to make a graph. Using your graph, what would you guess is the equation of the tangent plane at the point where x = 1 and y = 2? Why? (b) Use derivatives to compute the equation of the tangent plane described in part (a) and compare to your guess in (a).