Find the extremum of binary function f (x, y) = x ^ 2 + y ^ 3 + 4x-3y + 4, and explain whether it is a maximum or a minimum

f(x,y)=x^2+y^3+4x-3y+4
From f'x (x, y) = 2x + 4 = 0
f’y(x,y)=3y^2-3=0 x=-2 y=1,-1
f''xx(x,y)=2
f''xy(x,y)=0
f’'yy(x,y)=6y
AC-B ^ 2 = 12Y > 0 has extremum
F (- 2,1) minimum

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