1) Let f(x; y) = x^2 + y^3. Find the slope of the line tangent to this surface at the point (-1,1) and

lying in the (a) plane x = -1 (b) plane y = 1.

2)Show that the function f(x; y) =2x^2*y/x^4+y^2

has limit 0 along every straight line approaching

(0; 0). Prove also that the limit does not exist.

3)Find the limits

(a) lim x-x*y+3/x^4+5x*y-y^3

(x;y)!(0;0)