Hey All,

how do determine the position and nature (i.e minimum, maximum or saddle point) of the stationary points of the function.

f(x,y)=x^2 - 4xy + y^3 + 4y

this is what I have done so far

dz/dx= 2x-4y

dz/dy=-4x+3y^2+4

d^2z/dxdy=-4

how do you complete the question?

thanks