fA[x_,y_,n_]:=-((4/3)((n-1)(y^(-3/2))+(x^(-3/2)))-2((n-1)(y^(-1))+(x^(-1)))+11);
fa[x_,y_,n_]:=-(5x+9(x^(1/2))-(3+(2/3)(1+(n-1)(x/y))));
fo[x_,y_,n_]:=-(5y+9(y^(1/2))-(3+(2/3)((y/x)+(n-1))));

fA[x,1,n]//Simplify
fa[x,1,n]//Simplify
fo[x,1,n]//Simplify

n=3;
n=3;
Plot3D[{fA[x,y,n],fa[x,y,n],fo[x,y,n]},{x,(10^(-2)),2},{y,(10^(-2)),2},PlotRange->All,AxesLabel->{"x=(Subscript[α, A])/(Subscript[α, a])","y=(Subscript[α, A])/(Subscript[α, o])"},PlotLegends->{"fA","fa","fo"}]
Plot3D[{fA[x,y,n],fa[x,y,n],fo[x,y,n],0},{x,(10^(-2)),2},{y,(10^(-2)),2},PlotRange->All,AxesLabel->{"x=(Subscript[α, A])/(Subscript[α, a])","y=(Subscript[α, A])/(Subscript[α, o])"},PlotLegends->{"fA","fa","fo","0"}]