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I am trying to findout maximum value of a equation of two variable

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NEELU GUPTA
NEELU GUPTA 2018-9-11
评论： NEELU GUPTA 2018-9-17
an = 1500;
bn = 0.0022;
Mn = 0.024;
gn = 10^-15;
mu_n = 3;
syms x y real
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])
subs(r,{x,y},{sol.x,sol.y})
subs(t,{x,y},{sol.x,sol.y})
subs(s,{x,y},{sol.x,sol.y})
A = r*t;
B = s^2;
if A>B
if r > 0
disp('minima');
else
disp('maxima');
end
elseif A < B
disp('no minima & no maxima');
else
disp('no solution');
end
subs(eqns,{x,y},{sol.x,sol.y})
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回答（1 个）

Walter Roberson
Walter Roberson 2018-9-13
subs() does not change the original variable unless you assign the result to the variable.

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