syms x y
a = ((y.*x^3)+(x.*y^3)-(1.69.*x.*y));
eqA_partial_diff_x = diff(a,x)
eqA_partial_diff_y = diff(a,y)
M = solve(eqA_partial_diff_x,eqA_partial_diff_y)
N = [M.x,M.y]
[m,n]=size(N)
eqA_double_partial_diff_x = diff(eqA_partial_diff_x,x)
eqA_double_partial_diff_y = diff(eqA_partial_diff_y,y)
eqA_double_partial_diff_y_then_x = diff(eqA_partial_diff_y,x)
x=N(:,1)
y=N(:,2)
eqA_double_partial_diff_x=subs(eqA_double_partial_diff_x)
eqA_double_partial_diff_y =subs(eqA_double_partial_diff_y)
eqA_double_partial_diff_y_then_x=subs(eqA_double_partial_diff_y_then_x)
syms x y
a = ((y.*x^3)+(x.*y^3)-(1.69.*x.*y));
eqA_fx = diff(a,x)
eqA_fy = diff(a,y)
M = solve(eqA_fx,eqA_fy)
N = [M.x,M.y]
eqA_fxx = diff(eqA_fx,x)
eqA_fyy = diff(eqA_fy,y)
eqA_fyx = diff(eqA_fy,x)
D = eqA_fxx.* eqA_fyy - eqA_fyx^2
subs(D,{x,y},{N(:,1),N(:,2)})
Best Answer