I am trying to findout maximum value of a equation of two variable but there are some error

an = 1500;
bn = 0.0022;
Mn = 0.024;
gn = 10^-15; %channel gain from CBS to nth energy harvesting SU
mu_n = 3;
syms x y
eqns = Mn - mu_n*(1+exp(-an*(gn*(x + y)-bn)));
dx = diff(eqns,x);
dy = diff(eqns,y);
r= diff(eqns,x,2);
t= diff(eqns,y,2);
s= diff(dx,y);
sol = vpasolve([dx,dy])
r = subs(r,{x,y},{sol.x,sol.y})
s = subs(t,{x,y},{sol.x,sol.y})
t = subs(s,{x,y},{sol.x,sol.y})
A = [r].*[t];
B = [s].^2;
A = abs(A);
B = abs(B);
if A>B
if r > 0
elseif A < B
disp(‘no minima & no maxima’);
disp(‘no solution’);

Hi @neelu05,

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