3203.sagews

var('x,y',domain=RR)
f(x,y)=x+y+x*y-(x+y)^2
show(f)

\newcommand{\Bold}[1]{\mathbf{#1}}\left( x, y \right) \ {\mapsto} \ -{\left(x + y\right)}^{2} + x y + x + y

plot3d(f,(x,-5,5),(y,-5,5))

show(diff(diff(f,x),y))

\newcommand{\Bold}[1]{\mathbf{#1}}\left( x, y \right) \ {\mapsto} \ -1

show(diff(diff(f,y),x))

\newcommand{\Bold}[1]{\mathbf{#1}}\left( x, y \right) \ {\mapsto} \ -1

show(diff(f,x,2))

\newcommand{\Bold}[1]{\mathbf{#1}}\left( x, y \right) \ {\mapsto} \ -2

show(diff(f,y,2))

\newcommand{\Bold}[1]{\mathbf{#1}}\left( x, y \right) \ {\mapsto} \ -2