Find the maximum value of the function
on the disk x^{2} + y^{2} = 1.
Find the point on the surface
that is closest to the point (0, 0, 5).
Show that the curve
| x^{2} - y + z^{2} | = | 0 |
| x - y + z | = | 0 |
is an ellipse, and find the coordinates of its foci. (Recall that A_{1} and A_{2} are the foci of an ellipse E if the sum of the distance from P to A_{1} and the distance from P to A_{2} is is a positive constant as P varies through the points of E.