Probably the easiest way to explain this is to show you what I want to do. I want to draw a contourplot which shows the contour lines going through the points [0,-1] and [3/4,-7/16] (these are the expression's stationary points).  The values of f at each of these points respectively are 1 and 101/128, so I have tried to display these contours, but when the graph comes up, the contour lines don't go through the point [3/4,-7/16], although they do go through [0,-1]. The code I'm trying to use is below.

f(x,y):=x^3-3*x*y+2*y^2-3*x+4*y+3;

u:=pointplot({[0,-1],[3/4,-7/16]},symbol=asterisk,color=[red,blue]);
v:=contourplot(f(x,y),x=-2..2,y=-2..1, contours=[1,101/128], grid=[100,100],color=black );
display(u,v);
 

Thanks very much