Please help with practice example problems 4, 5, and 6.

4.

Find the equation of the tangent plane to f (x, y) = 754:2 14xy + 143:2 having slope 14 in the positive x direction and slope 28 in the positive y direction. (Use symbolic notation and fractions where needed.) Find the points on the graph of z = xys + 8 y'] where the tangent plane is parallel to 9x + 5 y + 9z = 0. (Give your answer as a commaseparated list of points in the form (ak, *, *). Express numbers in exact form. Use symbolic notation and fractions where needed.) Let f(x, y, z) = 10x2 y2 + 522. Calculate V f(0, 3, 4). (Write your solution using the form (*,*,*). Use symbolic notation and fractions where needed.)