f(x, y) = If[5 - (x - 9)^(2) / 15 - (y - 5)^(2) / 14 > 1.5, 5 - (x - 9)^(2) / 15 - (y - 5)^(2) / 14]
A: (5, 5, 0)
fx = Derivative(f, x)
fy = Derivative(f, y)
a: f(x(A), y(A))
b: f(x(A), y(A))
t(x, y) = If[abs(x - x(A)) < 3 ∧ abs(y - y(A)) < 3, f(x(A), y(A)) + (fx(x(A), y(A)) * (x - x(A))) + (fy(x(A), y(A)) * (y - y(A)))]
g(x, y) = If[abs(x - 5) < 7 ∧ abs(y - 5) < 7, ((-(x / 4 - 1.25)^(2)) * (y / 4 - 1.25)^(2)) + 5]
g2(x, y) = ((x - 5) * (y - 5)) + 5
P_0: (x(A), y(A), g(x(A), y(A)))
c(x, y) = If[abs(x - x(A)) < 4.5 ∧ abs(y - y(A)) < 4.5, g(x(A), y(A))]