syms x yf=exp(x^2+2*y)f=exp(x^2+2*y);A=3*diff(f,x)+5*diff(f,y)subs(A,[x,y],[0 0])clcsyms zf=log(exp(x)+exp(z))-log(exp(x)+exp(y))A=5*diff(f,x)-2*diff(f,y)+diff(f,z)subs(A,[x y z],[0 0 0])clcf=(x^2+y^2+z^1)/(x+y+z);f=(x^2+y^2+z^2)/(x+y+z);A=diff(f,x)+diff(f,y)+diff(f,z)subs(A,[x y z],[0 1 0])d1=diff(f,x)d2=diff(d1,y)d3=2*diff(d2,z)d3=diff(d2,z)/4B=d3subs(B,[x y z],[1 1 -1])%%%%%%%%%%%%%%% c?c tr? t? do%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%f=x^3+y^3-6*x*y;fx=diff(f,x);fy=diff(f,y);S=solve(fx,fy)X=S.x,Y=S.yA=[0 0];B=[2 2];fxx=diff(fx,x);fxy=diff(fx,y);fyy=diff(fy,y);del=fxy^2-fxx*fyysubs(del,[x y],A)disp('diem dung (0 0) ko la cuc tri')subs(del,[x y],B)Ba=subs(fxx,[x y],B)f=x^3+y^3-6*x*y;subs(del,[x y],A)syms x yf=x^2+y^2-32*log(x*y)fx=diff(f,x);fy=diff(f,y);S=solve(fx,fy);X=S.x;Y=S.y;XYP1=[4 4];P2=[-4 4];P3=[4 -4];P4=[-4 -4];A=diff(fx,x);B=diff(fx,y);C=diff(fy,y);del=B^2-A*C;subs(del,[x y],P1)subs(A,[x y],P1)subs(del,[x y],P2)subs(A,[x y],P2)subs(del,[x y],P3)subs(A,[x y],P3)subs(del,[x y],P4)subs(A,[x y],P4)disp('bon diem dung deu la cuc tieu')%%%%%%%%%%%%%%%% Tch phn kp%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%syms x yy1=x-1;y2=9-x;y3=3*x-3ezplot(y1)ezplot(y2)ezplot(y1)hold onezplot(y2)ezplot(y3)solve(y1-y3)solve(y1-y2)solve(y3-y2)f=x-2*y;int(int(f,y,y1,y3),x,1,3)+int(int(f,y,y1,y2),x,3,5)f=1/(x^2+y^2);syms r phiX=r*cos(phi);Y=r*sin(phi);syms r phiX=r*cos(phi);Y=r*sin(phi);g=subs(f,[x y],[X Y])*rint(int(g,r,0,2*cos(phi)),phi,0,pi/2)g=simplify(g)