I need help with knowing how to do 7 problems so that I will be better prepared in my Calc 3 class:

1) f(x,y)=xy+x^3. a)Find df/du(1,2) in the direction of the point (not a vector) (3,4) b) Find max. directional derivative of f(x,y) at (1,2) c) df/du(1,2)=0 in what 2 directions (as unit vectors)?

2)df/du(2,3)=4/sqrt13 in the direction of vector <2,3>. And f/du (2,3) = -3/sqrt5 in direction <1,2>. Find gradient f(2,3)

3)Find cartesian equation for tangent plane to surface xyz=2 at (1,2,2)

4) a) Find the double integral (0,1;x^2,x) for xy dydx b) Reverse the order of integration in part a, and compute the resulting integral.

5) Reverse the order of integration in double integral (0,1;0,sqrty) f(x,y)dxdy+double integral (1,3;0,(3-y)/2) f(x,y)dxdy

6)Find the volume under z=4-x^2-y^2 and above the xy plane

7)Find double integral (1<=x^2+y^2<=4) for (x^2+y^2)^(3/2) dA