syms x yf=x^3-y^3+3*x^2+3*y^2-9*x ;fx=diff(f,x);fy=diff(f,y);[x0 y0]=solve(fx,fy,'x','y')ffx=diff(fx,x);ffy=diff(fy,y);fxfy=diff(fx,y);[x1 y1]=solve(ffx,ffy,'x','y')x0和y0是极值点,x1和y1是拐点
