a=0:0.02:1;
b=0:0.02:1;
a((a+b)<=1) = nan; % 按限制条件限制 a b 的值
b((a+b)<=1) = nan;
[x,y] = meshgrid(a,b);
Q=720-620*x-20*y;
mesh(x,y,Q);
hold on;
P=10+620*x+20*y;
mesh(x,y,P);
a=0:0.02:1;
b=0:0.02:1;
a((a+b)<=1) = nan; % 按限制条件限制 a b 的值
b((a+b)<=1) = nan;
[x,y] = meshgrid(a,b);
Q=720-620*x-20*y;
mesh(x,y,Q);
hold on;
P=10+620*x+20*y;
mesh(x,y,P);
