Peaks, Ridge, Passes, Valley, and Pits
A Slide Study of f(x,y)=Ax^2+By^2
Cliff Long
The American Mathematical Monthly, 83 (1976) 370–371.

MAT329
Andy Long, Fall, 2015

(* An Homage to My Father, Clifford A. Long (1931-2002) *)
Manipulate[
f[x_,y_]:=A x^2+B y^2;
scale=1;
pxmin=-scale;
pxmax=scale;
pymin=-scale;
pymax=scale;
Plot3D[f[x,y],{x,pxmin,pxmax},{y,pymin,pymax},AxesOrigin->{0,0},PlotRange->{-2,2},ViewPoint->{Pi, 1.970, 3.445},AspectRatio->1,AxesLabel->{"x","y","f(x,y)"},BoxRatios->{1,1,2}]
,{{A,-1,"A"},-1,1} 
,{{B,-1,"B"},-1,1} 
]